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NOT TO BE TAKEN FROM THIS ROOM 


A STUDY OF AUTOTEIPLOIDS AND TRISOMICS 


OF COMMON BARLEY, HORDSUM VULGARS L, 


E. R, Kerber 






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THE UNIVERSITY OF ALBERTA 


A STUDY OF AUT0TRIPL0ID3 AND TRISOMIGS 
OF COMMON BARLEY* HORDEUM VULGARE L. 


A DISSERTATION 

SUBMITTED TO THE FACULTY OF GRADUATE STUDIES 
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE 
OF DOCTOR OF PHILOSOPHY 


DEPARTMENT OF PLANT SCIENCE 

by 

Erich Rudolph Kerber 


EDMONTON^ ALBERTA 


APRIL* 1958 







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ABSTRACT 


Triploid plants of Hordeum vulgare L. were found in an F 2 
intervarietal hybrid population derived from colchicine treated F]_ plants 
and in a large nursery of the variety Gateway. Triploids occurred 
spontaneously in Gateway with an estimated frequency of one in 6000 plants. 
An attempt to produce triploids by crossing tetraploid with diploid 
Gateway was unsuccessful. 

At meiosis in the Gateway triploids univalents lying off the 
equatorial plate during metaphase I were found to be distributed on 
opposite sides of the plate at random. Furthermore, only univalents 
located on the plate at the completion of metaphase I lagged and divided 
equationally at anaphase I. At anaphase I the distribution of the extra 
set of seven chromosomes to the poles was found to be in a binomial 
frequency. Microcytes formed by diads located on the periphery of the 
cells at anaphase I behaved as independent minute cells in succeeding 
meiotic stages. 

Among the progeny of the triploids no aneuploid plants 
occurred with more than three extra chromosomes ; the majority were either 
diploid or were primary trisomics. Data were given on the fertility and 
on the transmission of the extra chromosome through the gametes of a 
number of trisomics. Four morphologically distinct primary trisomic 
types were described in Gateway. One of these was cytogenetically 
demonstrated to be associated with Linkage Group II and independent of 
the remaining known groups. 




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ACKNOVJLED SEMEN TS 


The writer expresses his thanks to the National Research 
Council of Canada for financial assistance in the form of a 
Studentship and Fellowship during the academic years 1954-55 and 
1955-56, respectively; he is also grateful for the patient guidance 
given by Dr* John Unrau throughout the course of the study. The 
writer also expresses gratitude to his wife, Florence, for typing 
the manuscript. 








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table: of contents 

Page 

INTRODUCTION . 1 

PART I • TRIPIDIDS 

REVIM OF LITERA1URE .•. 3 

Origin and Occurrence of Triploids . 3 

Morphology of Triploids ..... 7 

Meiosis in Triploids . 7 

First Division .. 7 

Second Division . 18 

Functional Gametes of Triploids . 19 

MATERIALS AND METHODS . 21 

OBSERVATIONS AND RESULTS . 22 

Occurrence of Triploids .. 22 

Experimental Production of Triploids . 23 

Morphology of Triploids . 23 

Meiosis in Triploids . 24 

Metaphase I . 24 

Behavior of Trivalents and Bivalents ... 26 

Behavior of Univalents . 29 

Anaphase I . 33 

Telophase I .. 43 

Interphase .. 44 

Second Division ... 45 

Viability of Pollen from Triploids .. 4S 

Fertility of Triploids . 49 

Progeny of Triploids . 52 












































TABLE OF CONTENTS (continued) 


Page 

DISCUSSION . 53 

SUiviMARY .. 62 

ERiijNOES .. 82 

PART II : TRISOMICS 

REVIEW OF LITERATURE . 64 

MATERIALS AND METHODS . 68 

OBSERVATIONS AND RESULTS . 69 

Morphological Characteristics of Primary Trisomics •... 69 

Fertility of Trisomics ... .. 72 

Transmission of Trisomics . 74 

Cytogenetic Identification of Gateway Trisomic T39 ... 76 

DISCUSSION . 78 

SUMMARY ... 80 

REFERENCES . 86 


























A STUDY OF AU TOTRIPLOIDS AND TRISOMICS 


OF COMMON ft a WJ.p.Y., iiORDLUk VULG-AkD L. 

INTRODUCTION 

Autotriploid plants possess three basic sets of homologous 
chromosomes, whereas diploids have two. Triploids^ - have been reported 
and studied in numerous genera. The investigations have dealt with their 
natural occurrence and their experimental production, the pairing 
relationships of the chromosomes at prophase, the behavior of trivalent 
complexes and univalents at metaphase and anaphase of meiosis, and with 
the chromosome numbers of functional gametes. Although these studies have 
made valuable contributions to the elucidation of chromosome behavior 
in general as well as to the cytogenetics of the species concerned, the 
results have been varied and often inconclusive, particularly with regard 
to the behavior of the extra set of chromosomes at meiosis. 

Common barley, Hordeum vulgare L., is a diploid having 14 
chromosomes. Reports on triploids of this species are relatively rare, 
and the behavior of their chromosomes at meiosis has been described in 
only one report. The usual experimental methods of obtaining triploids 
in other species have been found generally unsuccessful in barley. 

Among the aneuploid progeny produced by triploids, trisomics 
(plants with one chromosome in triplicate) have been of particular value 
in cytogenetic investigations. Since the genetic ratios for genes carried 
by the extra chromosome are modified, trisomics are useful for associating 
chromosomes with their respective linkage groups. This altered ratio 

1 


Hereafter the term ’triploid* refers to autotriploid. 









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technique has been successfully applied’to Datura , tomato, corn and tobacco, 
to mention a fevj plants. It is only recently that trisomies of barley 
have been obtained and utilized in this manner. 

According to published reports, four and possibly five of the 
barley linkage groups have been identified -with their respective 
chromosomes through the use of chromosome translocations and trisomies. 

To date, however, a complete series of the seven possible primary barley 
trisomies has not, apparently, been developed and made available to barley 
cytogeneticists• 

The discovery of a number of triploid plants in two field 
populations of common barley prompted the present study, the first part 
of which deals with the triploids and the second part with their trisomic 
progeny. 

The objectives in the first part of the study were 1) to 
determine the frequency and origin of triploids that occurred spontaneously; 
2) to attempt to produce triploids of barley experimentally; 3) to 
contribute further to the knowledge of the behavior of chromosomes in 
triploids, particularly of the extra set; and 4) to determine the frequency 
of the various chromosomal types among the progeny of the triploids. 

The objectives in the second part of the study were l) to 
describe the morphological characteristics of a number of primary trisomies; 
2) to determine the fertility of trisomies and the transmission of gametes 
with an extra chromosome; and 3) to provide evidence for the association 
of one trisomic type with its corresponding linkage group, which heretofore 
had not been definitely shown to be independent of the remaining groups. 




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PART I: TRIPL0ID3 

REVIEW OF LITERATURE 

Occurrence and Origin of Triploids 

Triploid plants have been obtained from suitable experimental 
crosses and from natural populations in which they occurred spontaneously. 

Triploids have been produced experimentally by crossing an 
autotetraploid with its related diploid in Datura (10, 12), Lolium 
(339) > Lycopersicum (l6), Petunia (2l), Primula (17, 19), Secale (25), 
and Zea (15, 47). In his extensive review Smith (56) cited no reports 
on triploids of common barley obtained by this method. Tsuchiya (63), 
however, produced a hypotriploid plant, 2n~ - 20, by crossing an 
artificially induced autotetraploid with its related diploid of the 
same variety. He further reported ( 64 ) a hybrid triploid obtained by 
crossing the same autotetraploid with Hordeum spontaneum nigrum (2n z 14). 
The latter is a wild species closely related to common cultivated barley. 

The success with which triploids are obtained by intercrossing 
autotetraploids with diploids depends on the species and the direction 
in which the cross is made. Blakeslee et al. (10), and Buchholz and 
Blakeslee (12) observed that in Datura, triploids were produced, from 
the small proportion of viable seeds obtained, only when the tetraploid 
was used as the female parent. The reciprocal cross was completely 
incompatible due to pollen tube growth failure. A similar relationship 
was found in Primula sinensis by Darlington (19). 

^ Throughout this study the symbols x 2n' and ‘n‘ refer to the zygotic 
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4 


When the autotetraploid of this species was pollinated by the diploid, 
pollen tube growth appeared quite normal. In another study involving 
the same cross Watkins (66) stated that fertilization failed to occur. 
However, apparently fertilization must have occurred rarely since 
Darlington obtained triploids from this cross. In the reciprocal 
cross 2x^ pollen tubes were not functional in the style of 4* plants. 

Randolph (43) found that in the cross 2x X 4x of Zea mays 
about 98 per cent of the seed was abortive and less than 0.5 per cent 
of the relatively well-filled seeds were viable, while the reciprocal 
produced seed with a viability of less than five per cent. Cooper (15) 
studied the development of the caryopsis of these reciprocal crosses 
and concluded that the high degree of incompatibility was not due to non¬ 
fertilization but to failure of the caryopsis to reach a germinable stage; 
endosperm development was abnormal and the embryo suffered from a lack 
of nutrients. More normal development was noted in the 4x X 2x cross 
than in the reciprocal. Triploid plants were obtained from seed of both 
combinations. 

According to Chin (14), when autotetraploid rye was pollinated 
with the diploid, pollen tube growth was normal, and approximately 38 
per cent of the florets set seed. The incompatibility of the reciprocal 
cross was attributed to growth failure of the pollen tube. On the other 
hand, Hakansson and Sllerstrom (25) found that in their stocks of rye, 
fertilization occurred regularly in both combinations of the tetraploid 
and diploid. However, only four triploid plants were obtained from 783 

The symbol ’x‘ refers to the basic haploid chromosome number of a species. 





5 


tetraploid florets pollinated -with the diploid and the same number from 
1275 diploid florets pollinated with the tetraploid. The almost complete 
incompatibility in these matings was attributed to irregular development 
and disintegration of the endosperm. Endosperm development was somewhat 
more normal in the 4& X 2x cross, which probably accounted for the slightly 
greater success of this combination. 

Seed collapse following crosses between diploid and autotetraploid 
races of Lycopersicum pimpinellifolium was studied by Cooper and Brink (16). 
They concluded that incompatibility of 2x X 4x and 4x X 2x crosses was not 
due to triploidy as such but to conditions surrounding the triploid 
embryo within the seed. The occasional triploid obtained from the 4x X 2x 
combination exhibited normal vegetative growth. 

The spontaneous occurrence of triploids in diploid populations 
has been noted in Canna (66), Lycopersicum (30, 50), Nicotiana (22), 

Tulipa (42), Zea (33* 49), and in several genera of Qramineae » including 
Avena, Hordeunij Saeala and Tr.iti.num ( 28 , 29, 36, 37). The relative 
frequency in which they appeared has been determined in a few cases. 

Lesley (30) found from one to 0.4 per cent triploids in two different 
varieties of tomato. In the same species but different varieties Rick (50) 
calculated a frequency of one triploid in about 1200 plants, or less than 
2.08 per cent, and observed variation in frequency from season to season 
within the same variety. 

Triploids have occasionally occurred as members of twin seedlings. 
Muntzing (37) found that of 2201 twin seedlings from 14 genera, including 
Avena, Hordeum, Secale and Triticum , 2106 were diploid, while 95 had 
deviating chromosome numbers of which 77 were triploid. From the data 
of all species investigated there was noted a distinct tendency for one 



















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member of a heteroploid "twin to be triploid. The frequency of twins in 
eight varieties of Hordeum vulgare was found to be about one in 5900 
seedlings, and one twin member of 93 examined was triploid. Aase (2) 
and Kostoff (28) have suggested that the frequency of twinning is 
genetically controlled since it varies between species and between 
varieties. 

Several methods of origin have been proposed for the spontaneous 
occurrence of triploids: 

1. They have occurred through natural intercrossing of tetraploids 
and diploids found within the species. The various aspects of this method 
have been discussed above. 

2. A commonly supposed origin is the union of an unreduced with 
a reduced gamete of an otherwise normally behaving diploid plant. 

Unreduced gametes may be the result of failure of one of the meiotic 
divisions. 'That such unreduced gametes are formed has been rather 
definitely demonstrated cytologically (2, 8 , 9* 35* 42* 66). Syndiploidy 

' has been suggested as a further source of gametes with the diploid 
chromosome number (20). This is the failure of separation of daughter 
nuclei in divisions immediately preceding meiosis. It is thought that 
fusion takes place after the pachytene stage of meiosis, since usually no 
quadrivalents are produced. Aase (2) noted that pollen mother cells with 
multiple euploidy were not infrequently found in routine studies of anther 
material. It is logical to assume that similar phenomena occur to form 
doubled egg cells. Puick (50) noted considerable variation from season to 
season in the frequency of spontaneous occurrence of triploids in the same 
variety of tomato and suggested that high temperatures during the growing 














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season possibly influenced the production of diploid gametes. The fusion 
of a reduced with an unreduced gamete has been inferred as the method of 
origin of triploidy in Canna (5), Lycopersicum (30, 50), Tulipa (42), 
and Zea (33, 46). 

3. A third possible method suggested for the origin of triploids 
is the fertilization of an egg cell by two male nuclei (10, 22). 

4. The mode of origin of triploids from twin seedlings has 
been attributed to embryonal development of a fertilized endosperm 
cell or to a fertilized unreduced nucleus of a supernumary embryo sac. 

(2). According to Muntzing (36), a supernumary macrospore mother cell 
could give rise to an extra embryo sac having an unreduced chromosome 
number, which when fertilized by haploid pollen would result in a triploid 
zygote. 

Morphology of Triploids 

The morphological appearance of triploids varies from species 
to species. Lesley (30) noted that the stems, leaves, and flowers of 
triploid tomato were more or less gigantic, but the fruits were under¬ 
sized and few in number. Although triploid maize was observed to be 
more vigorous than diploid, there was no striking morphological difference 
(33). Lamm (29) found difficulty in distinguishing a triploid rye plant 
from normal diploids, the former being only slightly more vigorous. The 
triploid derived from crossing tetraploid common barley with the wild 
species Hordeum spontaneum appeared to exhibit heterosis ( 64 ). 

Meiosis in Triploids 

First Division 


According to the generally accepted hypothesis of pachytene 













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pairing, homologous chromosomes synapse at random as pairing segments; 
that is, only two chromosomes pair at one point (7, 20, 42, 58). Since 
triploids possess three homologous chromosomes of each kind, equal 
lengths of paired and unpaired chromosome segments should occur. The 
variation in number of chiasmata formed in these paired lengths 
determines the type of association observed at metaphase. If no 
chiasmata are formed between two particular chromosomes in the paired 
sectors, univalents occur. Studies of triploids of Kyacinthus (18, 20) 
and Tulipa (42) have indicated that the frequency of chiasmata formation 
is in proportion to the length of the chromosomes. Consequently, longer 
chromosomes are more likely to form trivalents and, for the same reason, 
more complex associations, while a relatively greater frequency of shorter 
chromosomes will occur as univalents. 

Myers (38) observed that at prophase of triploid Loleum perenne 
there was an excess of paired and a deficiency of single chromosome strands. 
However, never more than two chromosomes were associated at one point. 

The excess of paired strands appeared to result from pairing of normally 
nonhomologons segments. This form of illegitimate pairing evidently was 
not accompanied by ehiasma formation, since only trivalents, bivalents, 
and univalents occurred at metaphase in frequencies expected from normal 
pairing. 

Earlier papers on triploids of Canna (5), Datura (7), and 
Hyacinthus (6) reported that only trivalents were regularly observed at 
metaphase. However, more detailed later studies on these and other species 
indicated that bivalents and univalents also occurred (13, 17, 21, 22, 29, 
31, 33, 38, 39, 47, 63, 64, 65 ). Usually various combinations of 















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trivalents, bivalents, and univalents were found at metaphase ; the 
frequency of each varied from species to species and from cell to cell 
within the same anther* The combined total of trivalents and bivalents 
equalled the haploid chromosome number in true autotriploids ; pairing 
rarely occurred between chromosomes of the haploid or extra set. 

The five types of trivalent configurations that are 
theoretically possible from normal synapais of three homologues (20) 
are diagrammatically illustrated in Fig. 1. ‘The tandemr-chain and 
tandem - V types require a minimum of two chiasmata, one in each arm, 
while the triradial configuration also requires two chiasmata, both in 


TRIFLE- 

ARC 


RING- 

ROD 


TRIRADIAL 


TANDEM-V and 
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Fig. 1. Pairing arrangements of three homologous chromosomes at diplotene 
and resulting trivalent configurations at metaphase I. 


DIPLOTENE METAPHASE 













































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the same arm; the ring-rod requires a minimum of three chiasmata, two 
involving one arm and one the other, while two chiasmata in each arm 
produce a triple-arc association. 

In triploids of Datura and hyacinth Belling (7) found that 
short chromosomes with median centromeres formed any one of the 
trivalent configurations. Short chromosomes with subterminal centromeres, 
such as occurred in hyacinth, formed more complicated configurations 
because of interstial chiasmata. Long chromosomes with median centromeres 
tended to form ring-rod and both types of tandem coni’igurations. The 
ring-rod and tandem types were most frequently observed in Ganna (7)* 

Datura (7* 9), Hordeum (63, 64), iolium (36), Primula (17), and 3ecale (29), 
while triradial and triple-arc associations were rare or not found. 

The behavior of trivalents and bivalents at metaphase I 
has been found to be similar in most triploids and in other plants, 
such as autotetraploids, interspecific hybrids and aneuploids, in which 
they occur (l, 13, 18, 22, 24, 32, 33, 38, 41, 42, 43, 45, 47, 53, 65). 

Normally, at late diakenesis and early metaphase, when the nuclear membrane 
disappears, these associations move to the center of the cell and become 
oriented into an equatorial plate within the spindle mechanism. At late 
metaphase and early anaphase the trivalents usually disjoin two members 
to one pole and the third to the opposite, while the bivalent daughter- 
members separate one to each pole. According to some investigations, 
members of a trivalent may lag and divide equationally at anaphase (20, 36, 64 ). 

On the other hand, considerable variability has been found in 
the behavior of univalents. Since there are similarities of univalent 
behavior in triploids, interspecific and intergeneric hybrids, and 












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aneuploids, pertinent information from these sources will be discussed. 

The following general description of univalent behavior has 
been given by Darlington (20): "Unpaired chromosomes usually lie at 
random on the spindle at metaphase. They do not move towards the equator 
as early as the paired chromosomes. It is sometimes stated that unpaired 
chromosomes lying to one side of the plate are moving to the pole 
in advance of the bivalents at anaphase, but this conclusion is unjustifiable. 

Their position is due to their never having reached the plate, and they 
actually do not move until after the bivalents have divided. When the 
paired chromosomes begin to separate at anaphase unpaired chromosomes 
follow one of two courses: (l) those lying far away from the equator are 
included with the group of daughter bivalents passing to the nearest pole; 

(2) those lying near the equator move on to the plate, orientate themselves 
axially, and divide after a short interval into their two chromatids, 
which then pass to opposite poles as in mitosis," Based on Kihara's 
study of Triticum - Aegilops hybrids (Kihara, H. Genomanalyse bei Triticum 
und Aegilops . I and II. Cytologia, 2. 1931*)> Darlington concluded that 
univalent behavior was chiefly of the second type and that "variations 
commonly observed in univalent behavior are probably due to various degrees 
of delay in the movement of univalents relative to those of the bivalents." 

The behavior of univalents in wheat monosomies as described by 
Smith et al. (57) and Sears (55) was similar to Darlington's second type. 
However, numerous descriptions of their behavior in various triploids and 
interspecific and intergeneric hybrids have indicated that both types may 
occur in the same stock. 


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and Thompson (34) 9 and 'Thompson (59* 60) reported that univalent behavior 
in these hybrids followed a generally consistent pattern. At metaphase 
the univalents were more or less scattered throughout the cell, a few 
being observed near or on the plate together with the bivalents. After 
division of the bivalents the majority of univalents moved to the equator 
and divided equationally, the two halves separating to opposite poles. 

The remaining univalents did not move to the plate but joined the bivalent- 
halves at the nearest polar group. Thus, late anaphase polar groups 
consisted of bivalent-and univalent-halves and undivided univalents. 

Similar behavior of univalents was observed by Nishiyama (43) in an 
interspecific triploid hybrid of Avena and by Sax (53) in a pentaploid 
emmer - vulgare wheat cross. The latter paper also included a study of the 
hybrid Triticum monococcum X turgidum in which it was found that the 
univalents usually lay at or near either pole. In a few cases they moved 
to the plate and divided after the bivalents. This description is in 
contrast to that which has been given by Thompson (59) for the same hybrid, 
as already discussed, but involving different varieties. Sax and Sax (54) 
observed that in the intergeneric cross Aegilops cylindrica X Triticum 
vulgare the univalents remained at or passed to the poles without dividing 
at first division. 

Myers (40) and Myers et al. (41) concluded from observations 
of meiosis in diploids and autotetraploids of Lolium perenne , and several 
other grasses, that some univalents were oriented on the plate with the 
bivalents and multivalents before anaphase and that others were scattered 
throughout the cell during metaphase but became oriented some time before 
completion of anaphase, after which they divided equationally. The few 












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unoriented univalents that -were left intact in the cytoplasm formed 
micronuclei later. The descriptions of univalent behavior in autotet- 
raploid Secale cereale that have been given by Chin (14) and O'Mara (45) 
agree closely with that for Lolium . 

Gajewski (24) developed a series of Geum interspecific hybrids 
with increasing numbers of univalents and studied their behavior at 
metaphase - anaphase. Considerable irregularity was found in their 
behavior. In two hybrids with the fewest number of univalents, two to 
seven univalents were rarely found on the plate at metaphase, and most 
passed undivided to the poles at anaphase. The remainder were left at 
the plate at late anaphase where they either divided or passed whole to 
one of the poles. In two hybrids with 14 and 21 univalents, respectively, 
the univalents were scattered over the whole spindle. Later they 
congressed at the equator to form a more or less regular ring about 
the plate. At anaphase, after separation of the bivalents, all of the 
univalents rested on the plate. Their division and movement was very 
irregular; some divided; others did not; and many were omitted from the 
daughter nuclei. In the fifth hybrid, possessing 42 univalents, three 
groups of chromosomes tended to be formed, one at each polar end and 
one at the plate composed of a few bivalents and univalents. After division 
of the bivalents at anaphase the behavior of the univalents depended on 
their position on the spindle. Those on it moved without change to the 
nearest pole, while those on the equator appeared to stretch but moved as 
whole bodies to the poles. Gajewski attributed the differences of 
univalent behavior in the different hybrids to l) differences in genotypical 
constitution (an important factor in meiotic pairing) and 2) to different 
numerical relationships between univalents and bivalents - the more 







14 


bivalents on the metaphase plate, the greater the proportion of univalents 
that became oriented at metaphase - anaphase, 

A discrepancy between the relative proportions of metaphase 
univalents and anaphase laggards can be calculated from the data given 
by Boyle and Holmgren (ll) who studied the hybrid between Agropyron 
trachycaulum (2n = 28) and Hordeum .jubatum (2n = 28). An average of 
13. & univalents occurred at metaphase, which was approximately one half 
of the entire chromosome complement, while at anaphase only 3*51 laggards 
were observed (this value is calculated from data given in Table IA of 
their report). In the amphiploid of this hybrid an average of 1.3 
univalents were observed at metaphase and 1.4 laggards at anaphase (3). 

The data from this hybrid and its amphiploid tend to substantiate 
G-ajewski's second conclusion. 

Most reports of univalent behavior in triploids, particularly 
those from early investigations, are largely descriptive. In triploid 
asters all of the univalents divided at first division (4)> while in 
Solanum tuberosum they lagged but did not divide (35). The absence of 
lagging at second division further indicated that in the latter species 
univalents seldom, if ever, divided at first division. Although lagging 
univalents occurred occasionally in triploid tomato, they rarely divided 
at anaphase (31). In triploid lilium Chandler et al. (13) found that 
univalents were usually together with the trivalents and bivalents at the 
plate. Most frequently they lagged and divided equationally at anaphase 
after the trivalents' and bivalents had separated. McClintock (33) stated 
that in triploid corn univalents oriented on the plate probably divided 
at the same time as the trivalents and bivalents, while lagging univalents 
separated later. More precise and conclusive information on univalent 



















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behavior in triploids has been obtained in more recent studies. 

Approximately 43 per cent of the lagging univalents of triploid 
rye divided at anaphase (29). In triploid Phleum pratense (44) an average 
of 4*68 univalents occurred at metaphase, but an average of only 1.81 
univalents lagged and divided at anaphase. According to the data given 
by Punjasingh (47) on triploid corn, approximately 49 per cent of the 
microsporocytes had one or more univalents at metaphase, while only 
about 25 per cent had one or more laggards at anaphase. The writer's 
calculations of Punjasingh's data indicate that about 55 per cent of all 
metaphase univalents lagged and divided equationally at anaphase. 

Tsuchiya (64) found an average of 2.33 univalents at metaphase of a 
- hybrid triploid barley and an average of 1.46 laggards at anaphase. Of 
the latter, about 36 per cent were calculated to be derived from "improper” 
disjunction of trivalents and the rest from univalents oriented on the 
equatorial plate at metaphase. The results indicate that in these 
triploids a relatively large proportion of metaphase univalents did 
not divide at anaphase. In contrast to this behavior, Myers (38) 
calculated that in triploid Lolium perenne an average of 1.33 laggards 
occurred at anaphase as compared with 0.93 univalents at metaphase. The 
excess of anaphase laggards was attributed to "improper 11 disjunction of 
trivalents. In triploid hyacinths Darlington (18) also attributed an excess 
of anaphase laggards when compared with the number of metaphase univalents 
to imperfect disjunction of trivalent associations, although no supporting 
data were given. 

In normal diploids the equational split at anaphase occurs 
simultaneously in all daughter-members of disjoined bivalents. They are 
then termed diads. Aase (l), Darlington (20), Gajewski (24)* and love (32), 









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16 


stated that the equational split occurred simultaneously in all unpaired 
chromosomes and disjoined members of bivalents* In contrast to this 
behavior Myers (38) noted that many univalents oriented on the metaphase 
plate showed the 'split* before initiation of anaphase, while those off 
the plate did not* Aase (l) concluded from her studies on the cytology 
of numerous cereal hybrids that "The behavior of the univalents depends 
largely on their location on the spindle at the time of the equational 
split. The equational split may, however, overtake them at any location 
on the spindle, and consequently, if many univalents are at the equator 
at this critical time many univalents will divide.” 

It is generally assumed that univalents of aneuploids and 
interspecific hybrids and the extra set of chromosomes in triploids, 
whether they occur in associations as trivalents or unassociated, are 
distributed at random to the poles during meiosis (20). Some authors 
have claimed or assumed random distribution of univalents in certain inter¬ 
specific gramineous hybrids without giving statistical data (l, 27, 43, 

53, 54, 60). O'Mara (45) also assumed randomness of univalents in 
tetraploid rye. Anaphase distribution of chromosomes in triploid corn 
"appeared” random (45)* Although Tsuchiya (64) presented data on the 
observed distribution of the chromosomes at anaphase of triploid barley 
no statistical comparison with a binomial distribution was given. Visual 
inspection of his data indicates that several distribution classes were 
not in accordance with randomness, perhaps because of the relatively 
small numbers of cells recorded. Chromosome distribution at anaphase has 
been described as approaching or resembling randomness by comparing, without 
statistical tests of significance, observed frequencies with frequencies 




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17 


calculated according to the binomial in triploids of Ganna ( 5 ), Datura ( 8 ), 
Lycopersicuni (31 ) } and Zea (47)* 

To date the hypothesis of random distribution of the third set 
of chromosomes in triploids has been adequately tested in only two 
species. Satina and Blakeslee (51) recorded the distribution of 
chromosomes at first division in 1000 microsporocytes of triploid Datura 
stramonium (3x = 36). They found an excess of the more extreme anaphase 
groupings, 12 - 24 , 13 - 23 , 14-22, 15 - 21 , and a deficiency of the intermediate 
groupings, 17-19 and 18 - 18 . The discrepancies were statistically 
significant. The authors concluded that "Despite the lack of direct 
evidence from other forms than Datura , it seems probable that the 
divergence of the assortments at the I division in P.M.C. from calculated 
values is of general occurrence and is to be attributed to the nature 
of chromosomes and the mechanisms involved in their movements at 
division." Myers (39) tested the randomness of chromosome distribution 
at anaphase of triploid Loliurn perenne (3x = 21). The statistical 
■treatment of the data obtained from 2,494 metaphase and 1636 anaphase 
microsporocytes indicated that 1 ) at metaphase "unoriented univalents lie 
in the microsporocyte at random relative to one another and to the 
equatorial plate", and 2 ) "The distributions at anaphase I also were 
consistent with the hypothesis of chance position of the unoriented 
metaphase I univalents and random assortment of the extra chromosomes of 
the trivalents." Thus, the behavior found in triploid Loliurn differed 
from that in triploid Datura. 

Descriptions of univalent behavior during the stage from late 
anaphase to early interphase were similar in several papers reviewed. In 












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Triticum (53, 60) and Avena (43) interspecific hybrids, autotetraploids 
of Secale (45) and Loliurn (4l)* as well as triploid Lilium (13), the 
univalents that were oriented at the plate divided after the bivalents 
and other associations. The resulting univalent-halves usually moved 
to opposite poles in time to be included in the polar groups at telophase; 
if not, they were excluded to form micronuclei in the cytoplasm. 

Aase (l) and Kelburn and Thompson (34) occasionally observed that after 
division of a univalent lying off the plate both daughter-halves moved 
to the same pole. Chromosome fragmentation has been attributed to 
misdivision of lagging univalents at telophase (32, 55) and to lagging 
univalent-halves being cut into two by cell wall formation at early 
interphase (18, 42, 63). Univalents beyond the influence of the spindle 
have been observed to form microcytes on the periphery of the cell 
(7* 13* 14* 16, 23, 33* 34* 64 ). 'The univalent within such microcytes has 
been found to carry on division and pass through stages comparable with 
the two main daughter cells (16). 

Restitution nuclei formed at the conclusion of first division 
have been observed in triploids of Datura (8, 9) and Tulipa (42). 

Second Division 

Myers (40) and Smith et al. (57) observed that at second division 
all diads usually aligned to form an equatorial plate in each daughter 
cell and then divided equationally. The univalent-halves, derived from 
the previous division of univalents, lagged at the equatorial region 
during anaphase - telophase and either moved to the poles or were excluded 
to form micronuclei. In Avena hybrids (43) and in several other grasses 
that possessed univalents (41) some of the diads and univalent-halves 
remained at the poles to be included in the nuclei at telophase. Lagging 


















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univalent-halves have been observed to misdivide at telophase (55) • 

Without providing data Melburn and Thompson (34), Nishiyama (43), 

0 1 Mara (45), Sax and Sax (54), and Thompson (60) assumed that univalent- 
halves at anaphase - telophase passed at random to either pole. Muntzing (35) 
and Thompson (6l) noted that restitution nuclei occurred following 
second division. 

As a result of lagging chromosomes and their fragmentation 
at both divisions of meiosis a large proportion of the microspores of 
triploids have been observed to contain one or more micronuclei 
(13, 29, 38, 63, 64)* The proportion of ’good’ pollen has been found to 
vary among different triploids. From eight to nine per cent of triploid 
Lilium pollen germinated on artificial media (13), while from five to 
15 per cent of triploid Datura pollen germinated on 3x stigmas (12). 
Approximately 92 per cent of the pollen of triploid corn (47) and 
54 per cent of the pollen of triploid barley ( 64 ) was found to be well 
filled with starch. Similarly, the fertility has been noted to vary. 

Triploids of Lycopersicum esculentum (31) and Secale cereale (29) were 
completely self-sterile. Selfed triploid Lilium . (13) had 20 per cent of 
the fertility of the diploid. Tsuchiya ( 64 ) found a seed set of 19 per cent 
on open-pollinated triploid barley ; the fertility was increased by hand- 
self ing and by crossing with pollen from diploids. Punjasingh (47) 
determined that 11 per cent of the florets of triploid corn set seed, 
presumably when open-pollinated. 

Functional Gametes of Triploids 


In all reports reviewed (8, 12, 21, 22, 26, 30, 33, 38, 47, 51, 














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52 , 63) a marked discrepancy was noted in the frequency of the chromosome 
numbers in functional pollen and eggs of triploids when compared with a 
binomial distribution. These included triploids in which distribution 
of the chromosomes to the poles at meiosis had been found to be random. 

The number of extra chromosomes in functioning gametes has been found to 
vary among species. It has also been noted that extra chromosomes were 
transmitted with a higher frequency through female than male gametes 
(12, 22, 33)* In triploids of Zea (33* 47) and Petunia (21) pollen with 
the haploid number or with one extra chromosome functioned exclusively, 
except for the occasional one with the diploid or near diploid complement. 
Pollen of triploid Secale (29) and triploid Lycopersicum (31) was 
nonfunctional on both 3x and 2x stigmas. Functional eggs of triploids 
of Datura (8, 12), Lolium (38), and Lycopersicum (30) were found to possess 
up to two or three extra chromosomes. In addition to these extra 
chromosome types, a relatively low proportion of the functional female 
gametes of triploid Nicotiana (22) and triploid Zea (33* 47) had 
•intermediate numbers ranging between the haploid and diploid complement. 
Some triploids, therefore, tended to have progeny with chromosome numbers 
approaching almost exclusively the diploid number, while others produced 
additional types having intermediate numbers of the entire possible range 
but with a much lower frequency than theoretically expected. 











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MATERIALS AND METHODS 

The triploids described in this study were obtained from two 
sources. Three triploid plants were found in a large F 2 field population 
derived from intervarietal F]_ hybrids, which as germinating seeds had 
been treated with colchicine. Another group of 13 were found among 
4500 progeny head-rows of a highly homozygous line of the variety 
Gateway which had been treated with various antibiotics, fungicides and 
insecticides in the previous generation. The original objective of this 
material was to test the mutagenic properties of these compounds. All 
but three of the triploids were discovered during the flowering period 
because of their high sterility, exhibited at this stage by the open 
florets. The three triploids of hybrid origin, and 10 of the Gateway 
triploids were eytologically identified by chromosome counts of pollen 
mother cells or of mitotic divisions in ovary tissue. 'The remaining 
three, detected at harvest time because of their very low seed set, were 
assumed to be triploid since they produced aneuploid offspring similar to 
those obtained from the eytologically proven triploids. 

Secondary tillers were collected from the Gateway triploids for 
cytological study of microsporocytes. They were fixed in Carney 1 s 6:3:1 
at room temperature for two to three days and then stored under refrig¬ 
eration in the same solution for periods up to 15 months before being 
examined. 

Temporary aceto-earmine preparations were made for studying 
chromosome behavior. Mature pollen grains were stained with an iodine 
solution to determine the proportion of ’good' pollen. 















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Cytological data were recorded for three or four of the Gateway 
triploid plants. Although data for each were recorded separately, no 
attempt was made to analyze them individually because of insufficient 
material available from any one plant. Only those metaphase I and 
anaphase I cells in which all chromosomes and their associations could 
be clearly distinguished were recorded. Similarly, only microspore 
tetrads with the surrounding wall intact were recorded. 

Seeds harvested from the triploid plants were sown either in 
pots in the greenhouse or in field plots. Chromosome numbers of the 
resulting progeny were determined by counts in pollen mother cells or in 
somatic ovary tissue. The latter method was used because some of the 
plants tillered poorly and were highly sterile. To obtain a maximum 
number of seeds from these, a few florets only were removed for cytological 
examination from a head as it emerged from the leaf sheath. 

Microscopic observations and photomicrographs were made using a 
Ziess Cpton microscope fitted with apochromatic lenses and a reflex plate 
camera attachment. 


OBSERVATIONS AND RESULTS 

Occurrence of Triploids 

Three triploids were found among approximately 3000 progeny 
head-rows of an F 2 hybrid nursery derived from F^ plants treated with 
colchicine. One of the triploids was found among the progeny of a plant 
which also produced diploids and tetraploids, while the other two occurred 
in the progeny of different plants in which no tetraploids were observed. 





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Three of the 13 triploids found in the Gateway material occurred 
among check progeny rows. This would indicate that some of these triploids 
originated spontaneously* without treatment effect. Except in one case 
where two triploids came from the same mother plant* the sibs of all 
triploids were fully fertile* and therefore* presumably diploid. Wo 
attempt was made to obtain a reliable estimate of the frequency of 
occurrence of triploids among treated rows. However* an estimate was 
calculated for check rows. Four hundred and thirty-three check rows* 
which constituted approximately one tenth of the entire population* 
were closely observed plant by plant for sterility* as an indication 
of possible triploidy* several times during the flowering period and 
again at harvest time when low set of seed could be detected. Under this 
careful scrutiny three cytologically identified triploids were found at 
flowering time. 'The average number of plants per check row was estimated 
from an exact count of 82 rows. The total number of plants in the 433 
check rows was then estimated to be approximately 18*500. From this value 
‘the frequency of spontaneous triploids was determined to be about one 
in 6000 plants. 

Experimental Production of Triploids 

When it was observed that triploids occurred spontaneously in 
check rows, an attempt was made to produce them experimentally by hand- 
pollinating Gateway autotetraploids with diploids of this variety. One 
poorly developed* inviable seed was obtained from 242 pollinated florets. 

Morphology of Triploids 


The triploids were indistinguishable morphologically from diploid 


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24 


sibs. As stated previously, they were noted only because of the high 
degree of sterility characteristically evident at flowering time when 
the florets remained open for several days beyond that normally observed 
in diploids. Fig. 2 shows representative plants of diploid, triploid, 
and tetraploid Gateway. 

Meiosis in Triploids 

Observations were made on chromosome behavior at meiosis in 
microsporocytes at metaphase I and subsequent stages of the Gateway 
triploids. Data from several plants were combined for analysis. 

Iletaphase I 

At metaphase I the pollen mother cells contained various 
combinations of trivalents, bivalents, and univalents, as shown in Table I. 
The most common combinations were 6 -q-j + ljj + lj and + 2 tj + 2 j, each 

occurring with a frequency of about 30 per cent. No cells with 
P~~ T + + 7j were noted. 

All types of trivalents that are possible from normal pairing 
of three homologous chromosomes were observed - tandem-V (Figs. 4, 5, 7), 
tandem-chain (Fig. 7), ring-rod (Figs. 3, 4, 5, 6, 7, 8), triple-arc 
(Figs. 3, k) } and triradial (Fig. 5). Table II shows that slightly 
more than 50 per cent of the trivalents were the ring-rod type. The 
triradial type was least frequent, only 14 being observed in 865 cells. 

The bivalents were either closed or open, with 5*71 per cent being 
of the latter type. An average of 5.22 trivalents and 1.78 bivalents 
per cell occurred. 

In addition to the above expected associations of homologous 
chromosomes and their various combinations, the following unusual sorts 

















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TABLE I 

Frequencies of combinations of various chromosome 
associations at metaphase I 


_ Frequency _ ( _ 

Combination of % of 


associations _ No. of cells _ total cells 


7 III 



159 

14.96 

6 III 

+ lj-j- 

+ 1 i 

328 

30.85 

5 III 

+ 2 n 

+ 2 

I 

317 

28.82 

^III 

+ 3 n 

+ 3 i 

171 

16.09 

3 III 

+ k xi 

+ h 

69 

6.49 

2 m 

+ 5 n 

+ 5 

I 

15 

1.41 

1 iii 

+ 6 ii 

+ 6 i 

4 

0.38 


7 ii 

+ 7 i 

_0 

0.00 




1063 

100.00 


were observed among 1091 cells examined: 

1. A quadrivalent in each of three cells (Fig. 8). 

2. Three hexaploid cells (2n - 42) having only trivalents, 
bivalents, and univalents. 

3. One cell with an extra bivalent (2n = 23). 

4. Seven trivalents and a fragment in a cell. 

5. One microsporocyte deficient for three chromosomes (2n = 18). 

6. One cell with five trivalents, one bivalent, and four 
univalents (Fig. 7). 

7. Seven cells with a 1 side-by-side 1 , and seven cells with an 
'end-to-end 1 association of two univalents. These have been also termed 
pseudobivalents and secondary associations (46). These associations were 
observed to lie off the plate in all but one cell. 








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TABLE II 

Frequencies of various types of trivalents and bivalents 
observed in 865 metaphase I cells 




Frequency 

Configuration 

Total no. 

% of total 

Average per cell 

Trivalents 

Tandem-V 

1337 

29.63 

1.54 

Tandem-chain 

632 

14.01 

0.73 

Ring-rod 

2342 

51.89 

2.71 

Triradial 

14 

0.30 

0.02 

Triple-arc 

188 

4.17 

0.22 


4513 

100.00 

5.22 

Bivalents 

Closed 

1454 

94.29 

1.68 

Open 

88 

5.71 

.10 


1542 

100.00 

1.78 

Behavior of Trivalents and 

Bivalents.- 

At metaphase I the 


and bivalents usually were observed to form an equatorial plate. 
Occasionally one or two of these associations were seen to lie off the 
plate. Bivalent daughter-halves were oriented with the spindle fibre 
attachment regions toward opposite poles, while orientation of trivalent 
members depended on the type of configuration. Tandem-V, triple-arc, 
and triradial types were oriented two and one to opposite poles 
(Figs. 5 } 6, 7). Tandem-chain configurations were found to lie with 
a member oriented to each pole and the third member interposed between, 
unoriented (Fig. 7)* 'The ring-rod type was most frequently found to be 
oriented with two members toward one pole and the third to the other 
















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Fig. 2. Diploid, triploid and tetraploid Gateway* 
Fig. 3* Diakenesis with + 4tj 4* 4-- and 
showing triarc configuration (arrovj)* 

Fig. 4* Metaphase I cell with 7 ixi> one tandem-V, 
four ring-rod and two triple-arc (arrows) 
c onfigurations. 





















28 



Fig. 5. 

Fig. 60 
Fig. 7. 

Fig. 8 . 


Metaphase I with 3 t ^j + An + A ; two 
univalents on plate, one being ^ 
oriented; univalents off plate dis¬ 
tributed 0 - 2 . 

Metaphase 1 showing two triradial 
trivalents (arrows) and 1-1 
distribution of univalents. 

Metaphase I with 5jH + ijl + one 
tandem-V, and two ring-rod trivalents; 
one unoriented univalent on plate and 
three distributed 1-2 off plate. 
Metaphase I showing a quadrivalent 
(arrow)• 














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29 


(Figs, 4, 5> 6, 7)* Occasionally, however, the rod meniber of this type 
lay more or less parallel to the plate without orientation of the 
attachment region to either pole. 

Behavior of Univalents .- The position of the univalents in the cell 
varied considerably. They were observed to lie at the polar regions, in 
the vicinity of, or on the equatorial plate (Figs. 5, 6, 7). Those at 
the poles appeared to be oriented haphazardly, while those at the plate 
often were noted to lie parallel to it. Univalents not on the plate or 
at the polar regions were observed in various positions, extending from 
near the main group of equatorial chromosomes to the poles, randomly 
oriented. 

In order to determine the significance of the position of 
univalents in the cell at metaphase in relation to their subsequent 
behavior, the following information was obtained on univalents: 1) their 
position, on or off the plate: 2) orientation of those on the plate ; and 
3 ) the distribution to opposite sides of the plate of those not located 
on it. A univalent was regarded as being on the plate when observed 
to lie in the equatorial region. This region was considered to extend 
from one side of the cell to the other along the equatorial axis and 
approximately two thirds the length of a tandemr-chain trivalent along 
the polar axis. As an example, in Fig. 5 two univalents are on and two 
are off the plate. The position of some univalents was not clearly defined. 
These were more or less arbitrarily recorded into either group on the 
assumption that univalents so observed would be entered with equal 
frequency into both groups. For example, in Fig. 7 three univalents 
were recorded as off and one as on the plate. Univalents on the plate 
were further classed as oriented if lying more or less parallel to the 









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equatorial axis and as unoriented if in any other plane (Figs. 5* 7)* 

The proportion of univalents on the metaphase plate for each 
of the seven combinations of chromosome associations is given in Table III. 
The per cent of univalents on the plate in each class varied from 42.38 
to 23*00. The latter value cannot be regarded as reliable, since only 
four cells were recorded for this class of ljjj + 6^ + 6^.. The 
proportion of univalents on the plate in the remaining six classes 
ranged from 42.38 to 32.23 per cent. From the data in the table the 
average number of univalents per cell was calculated to be 1.74* and 
the average number of these on the plate was 0.66, or 37*73 per cent. 
Expressed in another way every 100 cells contained 174 univalents of which 
66 were on the plate. 


TABLE III 

Proportion of univalents on the plate at 
metaphase I 


Combination of 
chromosome 
associations 

Total no. 
of cells 
examined 

Total no. 
of 

univalents 

Univalents on 
plate 

ToF 

No. total 

7 m + °n + °i 

159 

— 

— 

— 

6 iii + hi + 1 i 

328 

328 

139 

42.38 

5 iii + 2 ii + 2 i 

317 

634 

234 

36.91 

4in + 3 JX + 3 J 

171 

513 

196 

38.21 

3 III + 4 II + 4 i 

69 

276 

89 

32.25 

2 III + 5 II + 5 I 

15 

75 

34 

45*33 

hn + 6 II + 6 I 


24 

6 

25 .OO 

Total 

1063 

1850 

698 

Av.37.73 











>: 




31 


For each combination of chromosome associations, univalents 
on the plate -were further classified as oriented or unoriented, as 
indicated in Table IV, The per cent of total univalents oriented on the 
plate ranged from 25.10 to 16.67* with an average of 20.52. It was 
calculated that an average of 0.37 oriented univalents per cell occurred 
or, stated in another way, 37 univalents in every 100 cells. Approximately 
54 per cent of all univalents on the plate were oriented. A summary of 
the data on the frequencies of the various classes of univalents is 
given in Table V. 


TABLE IV 

Proportion of univalents oriented on the 
plate at metaphase I 


Combination of 
chromosome 
associations 

No. of 
cells 

Total 
no. of 
uni¬ 
valents 

Univalents 
on plate 

Total No. 

no. oriented 

Oriented 

fo 

of total 

univalents 

fo of 

total 
on plate 

7 +0 

'iii ii 

+ 0. 

i 

117 

— 

— 

— 

— 

— 

6 m + x n 

+ 1 i 

243 

243 

100 

61 

25.10 

61.00 

5 m + 2 n 

+ 2 i 

246 

492 

187 

100 

20.33 

53.48 

4 TTT + 3 
III Ii 

+ 3 x 

135 

405 

155 

83 

20.49 

53.55 

3 +4 

III II 

+ 4 

I 

57 

228 

80 

38 

16.67 

47.50 

2 m + 5 u 

4 5 

I 

13 

65 

25 

13 

20.00 

52.00 

1 m + 6 n 

+ 6 I 

—4 

-2k 

6 

-k 

16.67 

66.67 

Total 

815 

1457 

553 

299 Av, 

.20.52 

54.07 























" 


■ 




> • ' ••• 













32 


TABLE V 


Summary of univalent classes at metaphase I 


Glass 

Frequency 


Per 100 
cells 

% of total 

univalents 

From Table III 



Univalents on plate 

66 

37.73 

From Table IV 



Oriented univalents 
on plate 

37 

20.52 


The proportions of cells having various numbers of univalents 
on the metaphase plate -was also recorded (Table VI), since, as -will be 
shown later, these may influence the proportion of anaphase cells with 
various numbers of lagging univalents. 


TABLE VI 


Frequency of metaphase I cells with 
various numbers of univalents on the plate 


No. of univalents No. of $ of total 

-qel. slate.CLalls cells, 


557 

52.40 

354 

33.30 

119 

11.20 

27 

2.54 

5 

0.47 

1 

0.09 

0 

0.00 

_ 0 

0.00 

1063 

100.00 


7 














33 


To test the assumption that univalents off the equatorial 

plate occurred on opposite sides of the plate at random, the observed 

distribution frequencies for each class of univalents off the plate can 

be compared with the calculated* For example, where two univalents 

occurred off the plate, they would be expected to lie on the same side 

(0-2 distribution) and one on each side (l-l distribution) in equal 

frequencies. Similarly, with three univalents off the plate the 1-2 

and 0-3 distributions would be expected in a 3il ratio. In cells with 

four univalents off the plate distributions of 0-4, 1-3 and 2-2 should 

2 

be expected in a ratio of 1:3*4. The X analysis for observed and 
calculated distribution frequencies for all classes of univalents off the 
plate is given in Table VII. In the table the data are arranged in 
classes according to the total number of univalents per cell, each of 
which is subdivided according to the number of this total that were off 
the plate. In all classes except one the fit of observed to calculated 
frequencies is satisfactory. The exception is for the class in which 
two univalents of a total of three occurred off the plate. A probability 
level of less than 0.01 indicates that the distribution of the 0-2 and 
1-1 classes deviated significantly from the expected 1:1 ratio. 

The data from all identical distribution classes in Table VII 
were combined so as to obtain a single test of fit of observed to cal¬ 
culated frequencies of the various distributions. For two univalents 
off the plate the fit to a 1:1 ratio of 0-2 and 1-1 distributions was 
poor (P = 0.02 - 0.01). This is due to the discrepancy, noted above 
in Table VII, for the class in which two of a total of three univalents 
occurred off the plate. The combined data for the distributions of 
three univalents off the plate (0—3 and 1-2) gave a good fit to a 1:3 



r . a-;?'! 

. 






■ • - 




















• 1 ■ • ■ 1 ' ; ; • 

’ 

- ; ' 

. , . . ■ . • > . . . ■ 

..... 

- 

. . j. a ■ ■ ■■ ; : 








- 

. ' 

; . : ?; .r ... 



.. . 



' 


■ 

;v«.i 





. 




. 





• ^ c 

! ... '/W ' ' 


. 

« 

■ 






















34 


TABLE VII 


X analysis of observed and calculated frequencies 
of distributions of metaphase I univalents to opposite sides 

of the plate 


Total no. of 
univalents 
per cell 

Univalents 

plate 

off 

No. of cells 


P 

Total 

no. 

Distri¬ 

bution 

Observed 

( 0 ) 

Calculated ( 0 -C) 

(C) C 

2 

2 

0 


2 

76 

67.00 

1.21 




1 

- 

1 


67.00 

1.21 







134 

134.00 

x 2 - 2.42 

0.20-0.10 

3 

3 

0 

_ 

3 

10 

12.00 

0.33 




1 

- 

2 

2S 

36.OO 

1.11 







46 

4B.00 

X 2 = 1.44 

0.30-0.20 


2 

0 

_ 

2 

44 

33.00 

3.67 




1 

- 

1 

22 

33.00 

3.67 







66 

66.00 

X 2 = 7.34 

<0.01 

4 

4 

0 

_ 

4 

3 

2 . 3 s 

0.16 




1 

- 

3 

10 

9.50 

0.03 




2 

- 

2 

6 

7.12 

0.18 







19 

19.00 

X?= 0.37 

0.70-0.50 


3 

0 

— 

3 

7 

5.25 

0.58 




1 

- 

2 

Jk 

Hill 

2M2 







21 

21.00 

X 2 = 0.77 

0.50-0.30 


2 

0 

_ 

2 

8 

10.00 

0.40 




1 

- 

1 

12 

10.00 

M2 







20 

20.00 

X 2 = 0.80 

0.50-0.30 


ratio (r =0.95 - 0.50). 

The data in Table VII were combined in a second manner to test 
the randomness of the distribution of univalents to opposite sides of the 
plate. Similar groupings of univalents, ie., 0, 1, 2, 3 } k> from each 




















35 


of the distributions, ie., 0-2, 1-1, 0-3, 1-2, etc., -were combined for 
all observed and calculated values, respectively, and then subjected to 

p 

a X analysis. A probability level of 0.10 - 0.05 for the combined 
data in Table VIII further substantiates the assumption of random 
distribution of univalents to opposite sides of the plate. 

TABLE VIII 

2 

X analysis of total frequencies of univalent 
groupings located off the plate at metaphase I 


Frequency 


Univalent 
grouping . 

Observed 

frequency 

... -(o) 

Calculated 

frequency 

. . CO .. 

{o=cf_ 

c 

0 

148 

129.63 

2.60 

1 

246 

281.25 

4*42 

2 

192 

175.99 

1.46 

3 

27 

26.75 

.02 

4 

616 

P = 0.10 

2.38 

6X6.00 

- 0.05 

.16 

2 

X = 8.66 


The overall results of the statistical analysis of the data 
on univalents occurring off the equatorial plate indicate that in 
general they -were distributed to opposite sides of the plate at random 
during metaphase I. 

Anaphase I 

At anaphase I all polar groups contained not less than seven 
diads nor more than 14. Presumably^ therefore, one chromosome from each 
bivalent and trivalent invariably moved to each pole. From zero to four 
univalents were observed to lag at the equatorial region after separation 































■ 



















. 








■ 




36 


and movement to the poles of the daughter chromosomes of the bivalents 
and trivalents. At this time all diads appeared equationally ’split’, 
■whether found at the poles or lagging at the plate (Figs. 9> 12). 

Lagging univalents usually divided equationally at late anaphase, and the 
daughter-halves then moved to the poles (Fig. 9* 13)* In a small proportion 
of cells lagging univalents were observed to misdivide (Figs. 10, 11). 

Also, in a few cells one and occasionally two univalents were noted to 
lie on the extreme periphery of the plate or polar group (Fig. 12), 
apparently beyond the influence of the spindle mechanism. These did 
not divide nor were they included in the main polar groups at anaphase 
or telophase (Figs. 12, 14). 

It was calculated above that for every 100 cells at metaphase I 
there were a total of 174 univalents. Of these 66 were on the plate, 

37 being oriented (Table V). From the data in Table IX it was further 
calculated that an average of 80 lagging univalents were present in 
every 100 cells at anaphase I, which is 45*97 per cent of the total 
number of univalents at metaphase I. This indicates that less than one half 
of the metaphase I univalents lagged and divided at anaphase I. Although 
this value is greater than the proportion of univalents on the plate at 
metaphase, that is 37*73 per cent (Table V), it does approach the latter 
value rather than 20.52 per cent (Table V), the proportion of oriented 
univalents on the metaphase plate. The evidence supports the assumption 
that all univalents on the plate at metaphase I, including those recorded 
as unoriented, lagged and divided at anaphase I. Presumably, univalents 
classed as unoriented became oriented by the time anaphase was initiated. 

The higher percentage of univalents found to lag at anaphase could be 
explained as the result of the recording system used. Conceivably, some 






















- 


■ 







•. 


....... 

.... . . ..... . . . 







. 

. 

■■..< i,;.. .;. iV'i;-; •• ..i. 







37 


of the univalents lying close to the plate, and recorded as off, later 
moved on to it and lagged at anaphase, after division of the bivalents and 
trivalents. . 

TABLE IX 


Frequency of anaphase I cells containing 
various numbers of lagging univalents 


No. of 
lagging 
univalents 
ner cell 

No. of 
cells 

% of 
cells 

Total 
no. of 
laggards 

0 

191 

48.23 

0 

1 

131 

33.08 

131 

2 

51 

12.88 

102 

3 

10 

2.53 

30 

4 

11 

2.78 

44 

5 

2 

0.50 

10 

6 

0 

0.00 

0 

7 

Q 

0.00 

0 


396 

100.00 

317 


Visual comparison of Tables VI and IX indicates that the 
proportions of cells with various numbers of univalents on the plate 
at metaphase I approach the proportions of cells at anaphase I with 
corresponding numbers of lagging univalents. On the basis of the 
assumption stated previously that only those univalents on the metaphase 
plate lagged and divided at anaphase and the evidence already presented, 
the observed frequencies of anaphase I cells with zero to five laggards 
(Table IX) were compared with frequencies calculated from the proportion of 
metaphase I cells having the corresponding numbers of univalents on the 










. 


. 












*-rj hr| hrj t-xj *ij 


38 


m 

1. ■ • - — - 

* 

% 

* 

d 

t 

W 

fy* * 


9 

10 £ 

■ 

m 



> 

H •* 







- * * 


* 

tv 



I 



11 









14 


Fig. 9* Anaphase I showing 8 - 11 distribution, one lagging diad, 
and two lagging daughter-univalents. 
ig.10. anaphase I with lagging univalent irdsdividing transversely, 
ig.ll. Anaphase I with two lagging univalents ndsdividing. 
ig.12. Anaphase I cell with two peripheral lagging diads. 
ig.13. Early telophase 1 with lagging daughter-univalents. 
ig.14* Telophase I cell showing appearance and location of 
peripheral diad. 























39 


o 

plate (Table VI). The X analysis of the data in Table X indicates a 

discrepancy between the observed and calculated values* The poor fit 

(P =< 0.001) is due almost entirely to the excess of cells observed in 

the classes with four and five laggards, as indicated by a probability 

level of 0*70 - 0*50 when the remaining classes were subjected to a 
2 

separate X test. The discrepancy may be due to the relatively small 
number of cells observed in the two classes and also, as previously 
stated, to error in the system used for recording the position of 
univalents as either off or on the plate at metaphase I, which could 
have contributed to an inaccurate estimate of calculated values. 


TABLE X 

2 

X analysis of observed and calculated frequencies 
of lagging univalents at anaphase I 


No. of lagging 
univalents 

Observed 

(0) 

Calculated 

(c) 

O 

O I 

o 

w 

0 

191 

207.50 

1.31 

1 

131 

131.37 

0.01 

2 

51 

44.35 

1.00 

3 

10 

10.06 

0.00 

4 

11 

1.86 

44.91 

5 

_2 

0.36 

7.47 


396 

396.00 X 2 = 

54.80 


P 0, 

.001 



The results nevertheless indicate that in the majority of cells 
univalents located on the plate at metaphase I lagged at anaphase I, 
after division of the bivalents and trivalents. 
















. 

. 

. 










- 




































40 


Cn the evidence already presented to indicate that the dis¬ 
tribution of univalents on opposite sides of the metaphase I plate 
tended to be. random (Tables VII, VIII) and on the assumption that the 
third member of a trivalent passed to either pole also at random, it 
appears valid to compare the observed frequencies of chromosome dis¬ 
tributions to the poles at anaphase I -with that expected for none and 
various numbers of lagging univalents, according to a binomial frequency. 
In cells with no laggards at anaphase the distribution of the extra 
seven chromosomes can be calculated from the expansion (g + g) . 

For cells with one laggard the distribution of the remaining six should 
be according to the expansion (g •+ g)^ 1 , for cells with two laggards 
(2 + 2)^ , f° r those with three laggards (g + for cells with four 

lagging univalents (g + g)^, and for those with five laggards (g + g)^. 

No cells with more than five lagging univalents were noted in 369 that 

were examined, ‘The observed and calculated frequencies of anaphase 

2 

distributions and analysis by the X method is presented in Table XI* 

No analysis is given for cells with five laggards, since there were only 
two in each category, one for each of the two possible types of dis¬ 
tributions, 7-9 and 8-8, which are expected in a 1:1 ratio. The 
results of the analysis indicate that the chromosomes were distributed 
to the poles in a binomial frequency, except for the category with two 
laggards. 'The discrepancy here is due to the 7-12 and 8-11 dis¬ 
tributions. When these were combined and tested with the remaining class 
a good fit of observed to calculated was obtained (P = 0.30 - 0.20). 

To test further the randomness of chromosome distribution at 
anaphase I, the observed data on the one hand and the calculated on the 
other from all distributions in Table XI were combined to form eight 


■ 




■ 












. 








■ 






41 


TABLE XI 

2 

X analysis of observed and calculated frequencies 
of chromosome distribution classes at anaphase I 


No, of 
laggards 

per cell_Distribution classes and frequency of cells 


0 


7-14 

8-13 

9-12 

10-31 

Total 


Observed (0) 

4 

23 

64 

100 

191 


Calculated (C) 

(0 - c r 

n 

2.99 

20.89 

62.67 

104.45 

191 


0.34 

0.21 

0.03 

0.19 

0.77 


O 

P = 

0.90 - 

0.80 



1 


7 - 13. 

8-12 

. .9. - 11 

10 - 10 

Total 


Observed (0) 

2 

24 

57 

48 

131 


Calculated (C) 

(0 - c) 2 

n 

4.09 

1.07 

24.56 

0.01 

61.41 

0.32 

40.94 

1.22 

131 

2.62 


o 

P - 

0.50 - 

0.30 



2 


7-12 

8-11 

9-10 

Total 



Observed (0) 

6 

9 

36 

51 



Calculated (C) 

3.19 

15.95 

31.87 

51 



(0 - C) 2 

p 

2.47 

3.02 

0.54 

6.03 




P a 

0.05 - 

0.02 



3 


7 - 11 

8-10 

9-9 

Total 



Observed (0) 

1 

8 

1 

10 



Calculated (C) 

1.25 

5.00 

3.75 

10 



(0 - c) 2 

p 

0.50 

1.80 

2.02 

4.32 




P - 

0.20 - 

0.10 



4 


7-10 

8-9 

Total 




Observed (0) 

4 

7 

11 




Calculated (C) 

(0 - c) 2 

n 

2.75 

0.56 

8.25 

0.19 

11 

0.75 





P = 

0.50 - 

0.30 










































































42 


possible polar chromosome groups. The number of chromosomes per group 

ranged in consecutive order from seven to 14. A probability level of 

o 

0.80 - 0.70 obtained from the X analysis of the combined data in Table XII 
indicates that the proportions of the various groupings occurred in 
frequencies expected from random assortment of chromosomes to the poles. 

TABLE XII 

Total frequencies of anaphase I polar chromosome 
groupings 


No • of _ Frequency 


chromosomes 
in group 

Observed 

(0) 

Calculated 
. (C) 

i2=sr 

c 

7 

18 

15.27 

0.49 

8 

73 

76.64 

0.17 

9 

167 

172.70 

0.13 

10 

244 

225.95 

1.44 

11 

167 

183.05 

1.41 

12 

94 

90.42 

0.14 

13 

25 

24.98 

0.00 

14 


2.99 

0.34 


792 

792.00 X 2 = 

4.12 


P = 0.80 

- 0.70 



The overall results of the analysis of chromosome behavior 
at anaphase I indicate that the extra set of seven chromosomes ■were 
distributed at random to the poles, whether they occurred at metaphase I 
as members of trivalent complexes or as univalents lying off the plate. 









. 






* 







« 













. 








. 

. 







43 


As mentioned previously in the general description of anaphase, 
a small proportion of cells contained univalents that behaved abnormally. 

In 396 cells examined, 13 were observed to have a diad lying on the 
periphery of the plate or pole. Apparently, these neither divided nor 
were included with the main group of polar chromosomes. Another four 
cells each had two diads similarly positioned. Altogether, 17 cells or 
4.29 per cent had one or two peripheral diads. Misdivision of lagging 
univalents was noted in two of 396 cells. In one (Fig. 10) a univalent 
was observed to misdivide transversely at the centromere to produce two 
equal-armed daughter-univalents. In the second cell two lagging univalents 
appeared to misdivide in a manner that would produce single-armed fragments 
or telocentrics. In another two cells the daughter-halves of an equationally 
split univalent were seen to move to the same pole. 

Telophase I 

At telophase I the microsporocytes contained two polar groups 
of chromosomes with from zero to eight lagging daughter-univalents located 
at various positions between (Fig. 13). In some cells one or two peripheral 
diads were again observed (Fig. 14). Also, in a few cells misdivision 
could be inferred from the centric and acentric fragments that were 
observed. 

The proportions of cells with various numbers of lagging 
daughter-univalents are given in Table XIII. The class with one lagging 
daughter-univalent was combined with that for two, since presumably one 
of two univalent-halves had already joined a polar group at the time of 
observation. The 'undetermined 1 class includes cells with irregular 
numbers of lagging univalent-halves and fragments that could not be 
definitely placed in the other classes. A legitimate comparison of 
observed frequencies of cells having various numbers of lagging daughter- 




. 

. 

. 


. 

• . 






- 










. 










■ 

. 






- 









44 


univalents -with expected frequencies calculated from anaphase I data 
cannot be made because of the relatively large number of undetermined 
cells. However, the proportions of cells with and without laggards 
can be validly compared. At anaphase I 4^.23 per cent (Table IX) and 
at telophase I 46.92 per cent of the cells showed no lagging. These 
values are in close agreement. 


table; xiii 

Frequencies of cells with various numbers of 
lagging daughter-univalents at telophase I 



No. 

of lagging daughter-univalents 



0 

2 

. L . 

Unde- 

6 8 termined 

. Total 

No. of cells 

198 

119 

31 

7 1 66 

422 

% of cells 

46.92 

28.20 

7.34 

1.66 0.24 15.64 

100.00 


Of the 422 cells examined 34* or 8.06 per cent, had one or two 
diads located at the periphery. Presumably these had remained in this 
position from anaphase through to the end of telophase. Misdivision of 
a univalent was observed or was inferred from fragments in eight cells, 
or in 1.90 per cent of the total. This value probably is somewhat less 
than the actual one because misdivision probably occurred in some of 
the cells classed as ‘undetermined 1 . 

Interphase 

At interphase two large nuclei were usually observed, one in 
each of the two daughter cells that resulted from first division. One 
and rarely two microcytes were associated with 51* or 9«17 per cent, 
of 556 pairs of interphase daughter cells that were recorded (Fig. 15). 







' 















* 














, 










. 






























45 


Each of two microcytes, associated -with different interphase cells, 
had two distinct minute nuclei. The remainder had one. Presumably, 
the microcytes were formed by diads previously observed on the 
periphery of anaphase and telophase cells. Approximately 57 per cent 
of the interphase microsporocytes contained no micronuclei, while 
one to six were observed in the remainder. An average of 0.67 
micronuclei occurred in each pair of daughter cells. 

Second Division 

The precise behavior of the chromosomes at second division 
could not be clearly observed in the material available. However, a 
general description can be outlined from the data obtained. 

At metaphase II diad chromosomes were aligned on the plate, 
often simultaneously in both daughter cells (Fig. 16). Univalents 
derived from equational division of lagging diads at anaphase I - 
telophase I were observed lying throughout the cell, off as well as on 
the plate. The few fragments that occurred usually were scattered in the 
cytoplasm. No lagging univalents or fragments were observed in 45*59 
per cent of the pairs of daughter cells examined. A single microcyte 
was associated with 8.05 per cent of the pairs of cells. Four of these 
21 microcytes had two diads and the remainder had one. All of the above 
metaphase II observations are based on data recorded from 261 pairs 
of daughter cells. 

At anaphase II, diads that were aligned on the equatorial 
plate separated and moved to the poles as in normal mitotic division 
(Fig. 17). Univalents were found lagging at the equatorial region 
in three of 27 pairs of daughter cells recorded. In each pair one 
laggard occurred in both daughter cells. Misdivision of lagging uni- 



. 


■ 












, 






. 







, 






. 




, 




. 

























. 


46 


valents was also noted in a few cells. 

During telophase II, daughter cells were observed to have a 
group of chromosomes at each pole and from zero to four univalents 
lagging in the equatorial region (Fig. 18). No laggards of any sort 
occurred in 54*BO per cent of 177 cells examined. Lagging univalents 
either l) misdivided at the plate (Fig. 18), 2) remained intact in the 
cytoplasm but were excluded from the main polar group (Fig. 19), 
probably to form micronuclei later, or 3) were included with the polar 
groups. Misdivision of a lagging univalent was observed in six pairs of 
daughter cells and inferred in another seven from pairs of fragments 
that were noted (Fig. 19). This indicates that misdivision occurred in 
a total of 7*35 per cent of telophase II pairs of daughter cells. Mis¬ 
division at anaphase I - telophase I was inferred from a fragment noted 
in each cell of seven (3.95 per cent) of cells. Five pairs were recorded 
with one to three fragments. In all of these observations, made on 177 
.pairs of daughter cells, the fragments were the size of univalent 
chromosome arms; hence, they probably originated from misdivision of 
lagging univalents at first and second division. 

At telophase II a microcyte was seen to be associated with 5.09 
per cent of the pairs of daughter cells (Fig. 20). The diad within the 
microcyte divided equationallv and the two halves moved to opposite ends 
of the minute cell, apparently following the same procedure as diads in 
normal cells. It was noted, however, that throughout second division the 
process lagged behind that in the main cells in passing through the stages 
of division. For example, in Fig. 20 the two main daughter cells are at 
late telophase while the microcyte is at the anaphase stage. 






• . 














. . 












■ 


















. 




















. 


■ ■ 

. 

' 


. 








. 




* 














,.'s tfg&fcvhb ^.y-'to^y 


. 




■ 


. ■ 










■ 

. 













hcj hij hrj *ij *Trj 


47 



Fig.15. Interphase cell illustrating attached microcyte with nucleus 
formed from single diad. 

Fig.16. Metaphase II with 10 diads in one and 11 in the other daughter 
cell. 

ig.17. Anaphase II daughter cell with 11-12 distribution. 
ig.18. Anaphase II - telophase II with misdividing daughter-univalent 
in each daughter cell. 

ig.19 Telophase II with lagging fragments and daughter-univalents. 

ig.20 Telophase II with divided diad in microcyte. 

ig.21. Tetrad with associated twin microcytes. 






















- 

- 

- 

. 

. • 

. - 

* 













48 


Tetrads were found to have from zero to nine micronuclei and 
an average of 1.81 per tetrad in 1346 that -were recorded. A minute 
microspore containing one micronucleus was attached to 2.30 per cent of 
the tetrads. Presumably these were formed from univalents and fragments 
that had been isolated in the cytoplasm at second division. 

At telophase II 54.80 per cent of the pairs of daughter cells 
had no lagging univalents or fragments. Assuming that laggards at this 

stage were the source of micronuclei in the tetrads, a similar or perhaps 
even greater proportion (because of laggards eventually included in the 
main nuclei) of tetrads should have occurred without micronuclei. Un¬ 
expectedly, however, only 29*72 per cent of the tetrads had no micronuclei. 

Microcytes initially formed from anaphase I peripheral diads 
were associated with 2.16 per cent of the tetrads. They now appeared 
as single minute cells, each with two nuclei, or as twin microspores, 
each with a micronucleus. These microcytes were enveloped together with 
the main group of four microspores by a common sheath (Fig. 21). The 
lower proportion of these microcytes observed at the tetrad stage (2.16 per 
cent) when compared with their proportions at telophase II (5.09 per cent) 
and anaphase I (8.06 per cent) can be explained by their separation and 
loss from the tetrad envelope during preparation of the slide, in spite 
of the care taken to avoid this. 

Restitution at second division was indicated in four cases by 
the association of one large microspore with two of normal size. 

Viability of Pollen from Triploids 
To obtain an estimate of the proportion of good pollen, nearly 









49 


mature anthers from secondary tillers of one triploid plant were treated 
with an iodine solution. Grains were classed as good if they appeared 
large, well filled with starch, unshrunken, and comparable to those 
observed in a diploid plant (fig. 22). The data in Table XIV show that 
there was considerable variability between anthers in the proportion of 
good pollen. The range was from zero to 21.3 per cent, the average 
being 5*5 per cent. Diploid plants grown under comparable conditions 
produced 98.7 per cent good pollen, figs. 23 and 24 give an indication 
of the types of grains that were formed in two anthers from tripioids. 


TABLE XIV 

Percentage of good pollen from 
triploid and diploid plants of Gateway 


Source 

Total no. 
of grains 

No. of 
good grains 

% good 
grains 

Diploid 

5200 

5132 

98.7 

Triploid 




Anther 1 

1013 

0 

0.0 

n 2 

672 

1 

0.2 

" 3 

1007 

22 

4*6 

" 4 

1010 

25 

4.0 

" 5 

561 

16 

2.9 

” 6 

1003 

49 

4.9 

7 

1108 

226 

21.2 

Total 6374 

349 Av 

. 5.5 


Fertility of Tripioids 


The fertility of all well-developed heads of open-pollinated 









hrj >xj 


50 



ig.22. Pollen 98 per cent good from diploid plant. 
ig.23. Pollen 2.54 per cent good from anther of 
triploid. 

Fig.24. Pollen zero per cent good from anther of 
triploid. 













. 

. 

* 

- 




wm 



. 












51 


triploid plants was calculated by expressing the number of seeds as a 
percentage' of the total number of florets. Data on the fertility of 
cytologically identified Gateway and hybrid triploids, Gateway triploids 
pollinated with diploid Gateway, and Gateway control plants are 
presented in Table XV. All plants were grown in field plots. 


TABLE XV 

Fertility of triploids and diploids 


Source 

No. of 
florets 

No. of 
seeds 

% 

fertility 

Open-pollinated 
Gateway triploids 

1413 

60 

4.2 

Gateway 3x x 2x 

142 

9 

6.3 

Ope n-pollinat ed 
hybrid triploids 

1024 

119 

11.6 

Cpen-pollinat ed 
Gateway diploids 

1531 

1470 

96.0 


The average fertility of 10 Gateway triploid plants was 4*2 per cent 
and of three hybrid triploids 11.6 per cent. Although these values are 
not directly comparable, since the triploids from the two sources were 
grown in different years, the hybrid plants on the average were more 
fertile. Ten diploid Gateway plants taken at random from the same plots 
as the triploids had an average fertility of 96.0 per cent. The data in 
Table XV indicate little difference in seed set between Gateway triploids 
that were open-pollinated and those hand-pollinated with normal diploid 
Gateway. 

Data on the viability of seeds from triploid plants are 
presented in Table XVI. Approximately 54 per cent of the seeds from 







. 

















. 











* 





. 
























. 

. 

, 



* 

. 





52 


the Gateway and 45 per cent of those from the hybrid triploids germinated. 
Although the germinability of the seed from the Gateway triploids was 
higher, the ultimate survival of the hybrid seedlings was about 50 per 
cent greater. 


TABLE XVI 

Viability of seed from triploids 





Adult plants 

Source 

No. of 

seeds planted 

Germination 

No • % 

No. 

% of 

germinated 

seeds 

Gateway triploids 

59 

32 54.2 

20 

62.5 

Hybrid triploids 

119 

54 45.4 

50 

92.6 


Progeny of Triploids 


The number of the various chromosome types recovered among 
the progeny of Gateway and hybrid triploids is given in Table XVII. 


TABLE XVII 

Chromosome constitution of progeny of triploids 


Source 

No. of 



No. 

of adult plants 



of seed 

seeds sown 

Total 

2 n 

2 n+l 

2 n+2 

2 n+3 

? n 

Other 

Unknown 

Gateway 

triploids 

81 

25 

5 

12 

5 


1 


2 

Hybrid 

triploids 

119 

50 

13 

26 

4 

2 


2 n*f(2) 

2 n+l+f 

2 n+2+f 

1 

Total 

200 

75 

18 

3B 

9 

2 

1 

4 

3 














































. 












* 


































53 


Approximately 38 per cent of the seeds that were sown produced mature 
plants• Of these, 24 per cent were normal diploids, and approximately 
51 per cent were primary trisomics. Three plants had three extra 
chromosomes; this was the maximum number of extra chromosomes found 
among the aneuploids. Four had a fragment in addition to one or two 
extra chromosomes. One plant was identified as triploid. In general, 
aneuploid plants with more than one extra chromosome were dwarfed, 
lacked vigor, had few tillers, and all but three of 12 plants in this 
catagory were completely self-sterile. Characteristics of 2n + 1 plants 
are described under the second part of this study. 


DISCUSSION 

The apparent difficulty in producing triploids of common 
barley experimentally is indicated by the paucity of reported attempts 
and the failure noted in the present study. Undoubtedly, the method of 
producing triploids of barley by intercrossing tetraploids and diploids 
has been unsuccessfully attempted numerous times and, consequently, 
has not been reported. Although Tsuchiya ( 64 ) was successful in 
obtaining a triploid by this method, his triploid cannot be considered 
a true autotriploid of common barley since the diploid involved was a 
closely related vvild species. Horde urn spontaneum . His success with this 
particular cross suggests that combinations between widely divergent, 
unrelated stocks of tetraploids and diploids of common barley are more 
likely to be fruitful as a source of triploids. Based on the few known 
attempts the conclusion can be drawn that crosses between tetraploids 







. 

. 

■ 

, 


. 

. 

• ' ■ 1 














. 

- 

o . . 









. 


54 


and diploids of common barley are highly incompatible. 

Barley triploids have been reported to occur spontaneously as 
members of-twin seedlings (37)* The present study has provided evidence 
that they occur spontaneously in another manner. Of three triploids 
found in a hybrid F^ population derived from colchicine treated F-j_ plants, 
one -was noted among the progeny of a mother plant that also produced 
diploids and tetraploids. Presumably, it originated from the union of 
a haploid and a diploid gamete produced by the treated mother plant. 

The other two triploids were descendents of treated F^ plants which 
otherwise produced only normal diploid offspring, as indicated by their 
normal fertility. Consequently, the mother plants of these presumably 
had produced only haploid gametes. Apparently, therefore, either 2x 
pollen from other nearby treated plants participated in fertilization 
or the two triploids were of spontaneous origin; that is, they were not 
the result of colchicine treatment. The latter supposition is more 
likely since it has been shown that 2x pollen usually does not function 
in 2x X 4x crosses (10, 12, 19, 14, 16). Further evidence to support 
the hypothesis of the spontaneous occurrence of triploids in this manner 
was provided by an additional 13 that were found in a nursery of 
approximately 4500 progeny head-rows of treated and untreated Gateway 
barley. Since three of these were found among the progeny of untreated 
mother plants, it is assumed that these and probably a portion of those 
from treated plants were of spontaneous origin. The sibs of all triploid 
plants but one were fully fertile and, therefore, presumably diploid. In 
the one exception two triploids were found in the same family. 

It is likely that none of these spontaneous triploids were 
derived from twin embryo seeds, since according to Muntzing (37) when 




' 






















































. ■ 






- 


•. .. .. .... 






. 


- 
























. ‘ y 














55 


one member is triploid the other is diploid and, consequently, completely 
fertile. All spikes produced by the triploid plants described in this 
study were highly sterile; hence, none could have been members of 
diploid-triploid twins. It is probable that they resulted from the 
fertilization of an unreduced by a reduced gamete produced by otherwise 
normal diploid plants. Cytological studies of several diploid species 
have shown that unreduced gametes are occasionally formed (2, 8 , 

35 9 42, 66). The writer has observed such gametes also in cytological 
studies of diploid barley. The evidence from the present and other 
studies further indicates that the triploid plants, described as being 
of spontaneous origin in this study, probably resulted from the 
fertilization of diploid eggs with haploid pollen produced by normal 
diploid plants; diploid pollen most probably was not involved since, as 
stated above, studies have shown that it rarely functions in the 
fertilization of diploid plants. 

Undoubtedly, triploid barley plants of spontaneous origin have 
been rarely observed in natural populations because of their close 
resemblance to normal diploids and the consequent difficulty in 
detecting them. 'The triploids described in this study were noted in 
field plots only because of their sterility which at the time of 
flowering was indicated by florets which remained open for an abnormally 
long period and by a very low set of seed on mature spikes. 

A higher proportion of trivalents and, consequently, lower 
proportion of univalents was found in the Gateway triploids than 
Tsuchiya noted in his triploid ( 64 )• These differences can be attributed 
to incomplete homology between the chromosome sets of the parents of 


'■ "1 ; 

. 


, - . c ■ : ■ ‘. 11 

- 

. 




' 























. 






' 


. 






. 

.al ■. • V;..‘ I v t :w • 

. . J . . V v.'. ’■ jdt ■ ‘ ft; ' .. I 

- 

























. . , 

■. 

■ 


. 














. 



















56 


Tsuchiya’s triploid, common barley and Hordeum spontaneum . 

Only three quadrivalents were noted in 1092 metaphase I cells 
of the Gateway triploids. This substantiates evidence obtained from a 
haploid ( 62 ) and a hypotriploid ( 63 ) to indicate that very little 
reduplication of chromatin occurs within the basic set of chromosomes 
of common barley. 

Univalents observed at metaphase I in the Gateway barley 
triploids were divided into two groups: l) those located off the 
equatorial plate and 2) those found on the plate. By means of suitable 
statistical treatment of the data it was shown that the univalents 
positioned off the plate were distributed on opposite sides of it at 
random. These results agree with those reported by Myers (39) who 
studied univalent behavior in triploid Lolium perenne . As might be 
expected the relative proportions of these two classes of univalents 
has been found to vary among different triploids (36, 39* 64 ). However, 
of more significance is the behavior of each group at late metaphase I 
and at anaphase I. In his study Myers (36) noted that an average of 1.33 
laggards per cell occurred at anaphase I, as compared with a total 
average of only 0.93 univalents per cell at metaphase I. He attributed 
this excess at anaphase to "improper" disjunction of trivalents. Although 
Tsuchiya ( 64 ) noted a much lower average proportion of laggards at 
anaphase I than of average total univalents at metaphase I (I .46 per cell 
as compared with 2.33)* he found that there was a greater proportion of 
anaphase I laggards than could be accounted for by the proportion of 
univalents located on the plate at metaphase I. He assumed that only 
univalents located on the metaphase I plate lagged and divided 
equationally at anaphase I and concluded that the excess of anaphase I 
















■ 




■ 


y* ■ "' ,• 
































- 






t - i •.!. 


- 

' L ! i • - 4 r . .- 

' ■ 


. 











. 

' - ■ • • : v;, 





.v v • 


•;. ■ :' ..!• . :.r 



. 












57 


laggards originated from "improper" disjunction of trivalents. The 

results from the present study indicate that trivalents were not a 

source of lagging univalents at anaphase I in Gateway barley triploids. 

An average of 0.66 univalents per cell were found on the plate at 

metaphase I and 0.80 laggards per cell at anaphase I. The difference 

between these values is considerably less than between the corresponding 

o 

values for Tsuchiya's triploid. A X test of observed frequencies of 
anaphase I cells with zero to five laggards and the expected frequencies 
based on the proportion of metaphase I cells with corresponding numbers 
of univalents on the plate indicated that there was close agreement for 
all but the two classes with four and five laggards (Table X). The 
number of cells observed in these two classes was too small (four per 
cent of the total) to permit a valid test. The average for the remaining 
four classes, having from zero to three univalents on the metaphase 
plate, and that for the corresponding classes of anaphase laggards was 
0.6 k univalents and 0.69 laggards per cell, respectively. Since these 
two values are in close agreement, the conclusions can be drawn that 
only those univalents located on the plate at metaphase I lagged and 
divided equationally at anaphase I and that members of trivalent 
associations were not an additional source of anaphase laggards. 

The assumption that the extra set of chromosomes in triploids 
is distributed to the poles at random during meiosis has been inferred 
in several studies of triploids but has been adequately tested in only 
two (37, 51> 52). In the present study the statistical analysis of the 
data obtained from a relatively large number of cells indicated that at 



- 


. 

■ 

* 

■ 

. 


. 

. .. ....... 

. If . ~ • • , : . ' . •' «, 1 . 

. 

. 

■ ' ■ > . . . 




5S 


anaphase I the chromosomes were distributed to the poles in a binomial 
frequency in all classes of cells, with and without lagging univalents. 
(Tables XI and XII). These results agree with Myers*(39) conclusions, 
based on a study of triploid Lolium perenne , that n the distributions at 
anaphase I also were consistent with the hypothesis of chance position 
of unoriented metaphase I univalents and random assortment of the extra 
chromosomes of the trivalents." That these findings do not have general 
application to all triploids has been shown by Satina and Blakeslee (51) 
in their detailed study of triploid Datura stramonium . They noted a 
statistically significant divergence of certain distribution classes 
from that expected according to random assortment at anaphase I. They 
concluded that ”it seems probable that the divergence of the assortments 
at the I division in P.M.C. from calculated values is of general occurrence 
and is to be attributed to the nature of the chromosomes and the mechanisms 
involved in their movements at division.” 

The results from the present and from previous investigations 
of triploids emphasize the caution to be taken in forming broad, general 
conclusions from a single study and also indicate the need for further 
intensive, detailed statistical analysis of chromosome behavior in 
triploids of other species. 

Although the precise behavior of the chromosomes was difficult 
to trace at second division in the material available for this study, 
a general pattern could be perceived. At metaphase II - anaphase II the 
diads formed an equatorial plate and divided equationally. Univalents 
derived from division of anaphase I laggards were either positioned on 
the plate or lagged in the cytoplasm at metaphase II. Subsequently 





































. 





59 


their behavior at anaphase II - telophase II followed one of three 
courses: 1) they were included with the polar groups; 2) they remained 
lagging intact in the cytoplasm, probably to form micronuclei later; 
or 3) they misdivided at the equatorial region in a small proportion of 
cells. As a result of the division of lagging chromosomes at anaphase I 
- telophase I and the subsequent lagging of daughter-univalents and 
fragments at second division, tetrads with an average of 1.81 micronuclei 
were formed. No micronuclei occurred in approximately 30 per cent of 
the tetrads. This is an unexpectedly low frequency when compared with 55 
per cent of the pairs of telophase II daughter cells that contained no 
micronuclei. 

Microcytes possessing one or two chromosomes have been observed 
associated with normal cells at meiosis in a variety of plants, including 
triploids of Datura (7), liliurn (13), hyacinths (18), Zea (33) and 
Hordeum ( 64 ). In the present study it was possible to follow the 
behavior of microcytes through all stages of both meiotic divisions. They 
originated at anaphase of first division from one or, less often, two 
univalents that were positioned on the periphery of the equatorial region 
or of a polar group of chromosomes. These univalents showed the typical 
anaphase ’split* but the halves did not separate. At telophase - interphase 
each peripheral diad formed a minute cell, although in rare instances two 
were seen together in a single microcyte. Each minute cell was attached 
to the microspore mother cell (Fig. 15). At second division the 
chromosome(s) in each microcyte divided equationally, and the resulting 
univalent-halves moved to opposite ends of the microcyte. At the 
completion of second division each microcyte had developed into twin minute 

















































. 

„ 


- 


- 





D 











60 


microspores that were attached to the main group of four (Fig, 21), 

These observations are similar to those reported in hyacinths (18), 

Lilium (13) and Triticum (23)* They indicate that a minute cell with 
a single chromosome is capable of independently undergoing division, 
exhibiting spindle activity and polarity during the process, and they 
add to the evidence for the autonomous nature of individual chromosomes 
during meiosis. 

Although the distribution of the extra set of chromosomes has 
been shown to be random or to approach randomness in a number of different 
triploids, in none has the frequency of functional eggs and pollen been 
found to correspond to the expected. Usually gametes with chromosome 
numbers approaching the haploid complement of the species were found to 
function most frequently. 'Those with intermediate numbers and numbers 
near the diploid complement functioned infrequently, rarely, or not at 
all. Furthermore, it has also been noted that there is usually a more 
pronounced selection against aneuploid gametes on the male than on the 
female side. The results of the study on triploid Gateway barley agree 
with these general observations in other species. On the basis of random 
assortment of the chromosomes at anaphase I, plants with 18 to 24 
chromosomes would be expected most frequently. It was found, however, 
that approximately 75 per cent of the progeny from open-pollinated 
triploid plants were diploids (14 chromosomes) and primary trisomics 
(15 chromosomes). Apparently, gametes vjith more than one extra chromosome 
functioned infrequently, and most probably these were female. The low 
frequency of progeny with more than one extra chromosome may be attributed 
to the following factors, assuming that chromosome distribution at 






' , , 




■ 


. 








. 
























. 

. . . ' . 


. 












, 





















. 







61 


macrosporogenesis 'was also random: l) Gametes with more than one extra 
chromosome were probably less viable than those with the haploid number 
of seven or with eight. 2) Male gametes with more than one extra 
chromosome were less viable than female gametes with the same number 
of chromosomes. 3) Male gametes with extra chromosomes probably failed 
to function in fertilization because of certation. 4) Aneuploid embryos 
with more than 15 chromosomes were probably less viable than diploid 

and trisomic embryos, as suggested by the low fertility of the triploids. 

5) Reduced seed germination and seedling lethality probably were 
further effects of 4)* 

A comparison of the fertility among the triploids from the 
two sources reported in this study and Tsuchiya's triploid would seem 
to indicate that fertility of triploids is influenced by the degree 
of heterozygosity. The average fertility of the triploid plants 
obtained from a highly homozygous stock of the variety Gateway was four 
per cent, of those derived from highly heterozygous, intervarietal 
hybrids about 12 per cent and of Tsuchiya’s interspecific hybrid triploid, 
produced from the cross between tetraploid common barley and the closely 
related wild diploid species, Hordeum spontaneum , 19 per cent. Thus, 
the triploid plants from the most homozygous stock were lowest in fertility, 
while the triploid from the interspecific hybrid was highest, despite 
the higher proportion of univalents found at meiosis in the latter. 






. u\OC' ■ 





■ 








. 






■ 







, 

- - - . ■ - - ■■■. 

. 


- 












j: • . v.\ •• s: ■ o';,i 

. 






. 




. 


. 


- 


- 




. 











62 


SUMMARY 

1. Three triploid plants were found in an F£ population of 
common barley derived from colchicine treated intervarietal hybrids. 

An additional 13 were found in a large population of the variety Gateway. 
Triploids occurred spontaneously in Gateway with a frequency of one in 
approximately 6000 plants; the origin of these was attributed to the 
fertilization of unreduced female gametes with reduced pollen produced 
by diploid plants. 

2. Morphologically, adult triploid plants were indistinguishable 
from diploids. 

3. An attempt to produce triploids by pollinating tetraploid 
Gateway with the related diploid was unsuccessful. 

4. At meiosis in the Gateway triploids an average of 5«22 
trivalents and 1.78 bivalents occurred. All types of trivalents that 
are. possible from pairing between three homologous chromosomes were 
observed. In addition, three quadravalents were noted in 1091 cells 
examined. 

5. It was statistically determined that univalents lying off 
the equatorial plate at metaphase I were distributed on opposite sides 
of the plate at random. 

6. 1? analysis of the data indicated that univalents located 
on the plate at the completion of metaphase I lagged and divided 
equationally at anaphase I. Univalents off the plate did not divide but 
were included with the nearest polar group at anaphase I. 

7. The distribution of the chromosomes to the poles at 
anaphase I was in a binomial frequency and, therefore, in accordance 






























■ 












. 































- 

« 










- 


- 






63 


with the hypothesis of random assortment. 

8. Misdivision of lagging univalents occurred in 1.90 per 
cent of telophase I cells. 

9. At second division diads divided equationally. Univalents 
derived from equational division of lagging chromosomes at anaphase I 
either were included with the main anaphase II polar groupings or 
lagged in the cytoplasm. Misdivision of univalents at telophase II 

was inferred in 3*95 per cent of the pairs of daughter cells. 

10. As a result of chromosome lagging and misdivision at first 
and second meiotic divisions, about 70 per cent of the tetrads had one 

or more micronuclei. 

11. Minute twin microcytes were associated with 2.16 per cent 
of the tetrads (Fig. 21). Each set originated from a lagging univalent 

located on the periphery of the cell at anaphase I where it formed a 
microcyte at telophase I - interphase I (Fig. 13). During second 
division the microcyte behaved as an independent cell; the enclosed 
univalent divided equationally to form daughter cells, each with a 
chromatid. (Figs. 20, 21). 

12. Pollen from one Gateway triploid plant averaged 5*5 per cent 

good. 

13. The fertility of open-pollinated Gateway and hybrid 
triploids was 4*2 and 11.6 per cent, respectively (Table XV). 

14. Approximately 54 per cent of the seed from the Gateway 
triploids and 45 per cent from the hybrid triploids germinated. 

15. Of a total of 75 offspring obtained from the triploids, 

24 per cent were diploid, 51 per cent were trisomic, and one plant was 
triploid. None of the aneuplcid plants had more than three extra chromosomes. 


* 

. 












- 


o 










'idD 


. 






. 
















.. 


64 


PART II: TRISOMICS 


REVISE OB’ LITERATURE 


The first trisomic plants -were described in Datura in 1919 
by Blakeslee and Avery (2), In 1920 Blakeslee et al*(5) reported that 
12 morphologically distinct trisomic types were found, corresponding to 
the haploid chromosome number of Datura , By means of the modified ratio 
technique Blakeslee and Farnham (4) identified the gene 'white 1 with the 
trisomic type 'Poinsettia'. Subsequently, genes were identified with 
each of the 12 trisomic types. Since these early reports on Datura , 
trisomics have been obtained and studied in Nicotiana (12, 16), tomato 
(17, IS, 19, 27), corn (21, 22), rye (30), and more recently in common 
barley (25, 28, 31)* 

McClintock and Hill (22) used trisomics to associate the gene 
X with the smallest chromosome pair of corn and also reported the ident¬ 
ification of trisomics with five additional linkage groups. Lesley 
(17, 18, 19, 20) first obtained 11 of the 12 primary trisomics in tomato 
and identified certain of these with specific linkage groups. More recently 
Rick and Barton (27), using different material, obtained the complete 
series of 12 primary tomato trisomics and cytogenetically identified six 
with the corresponding linkage groups. 

Trisomic plants have been obtained from several sources. 
Occasionally they have occurred in the progeny of normal diploids and 
presumed to have resulted from nonconjunction or nondisjunction at meiosis 
(7, 12, 30). A further source has been from the progeny of plants 
heterozygous for an interchange. Burnham et al. (ll), and Ramage (25) 
attributed the origin of these to a 3 ; 1 disjunction from a translocation 

























i 






- i U . t 



























' 







- 




. • • . . V. 













■ • . - •• * --•" 

... • 



65 


complex of four chromosomes and subsequent formation of gametes with one 
extra chromosome. The most prolific source, however, has been from the 
progeny of triploids (6, 8, 13, 14, 16, 18, 21, 23, 24, 27, 31). 

In most species the presence of an extra chromosome changes the 
phenotype of the plant. Usually a group of characters specific for each 
chromosome is altered. Thus, in Datura the 12 primary trisomic types 
were phenotypically distinct (l), as were those of Nicotiana sylvestris 
(l6) and tomato (27)* On the other hand, none of the chromosomes in 
corn produced distinctive morphological changes when in triplicate other 
than decreased size and vigor (21). Characters that have been observed 
to be modified by the presence of an additional chromosome include 
growth habit; plant height; shape, size, color and position of the leaf; 
thickness and stiffness of the stems; and enlargment or decrease in size 
of the floral parts and fruits. In addition, trisomic plants generally 
have been noted to be less vigorous than diploids and completely to 
partially sterile, particularly on the male side (16, 18, 21, 25 , 27, 31)* 

On the basis of random chromosome distribution to opposite 
poles at meiosis, gametes with the haploid number and with an extra 
chromosome should be produced by trisomics in equal frequencies. 
Furthermore, if both male and female gametes are fully functional, equal 
proportions of diploid and trisomic progeny should be produced. Actual 
transmission of the additional chromosome is, however, considerably less 
than expected and varies with the trisome involved. In Datura (3) 
transmission through the ovules varied from about three to 33 per cent; 
in tomato (27) from less than one per cent to about 25 per cent, and in 
corn from 22 to 52 per cent (15)* The frequency of transmission through 










66 


the pollen has been found to be considerably less than through the eggs. 
Under favorable conditions only five of the 12 primary trisomics of Datura 
were transmitted through male gametes (9). In Nicotiana sylvestris 
transmission through pollen varied from zero to 34 per cent, and in 
eight of 11 trisomics it was less than 10 per cent (16). In corn McClintock 
and Hill (22) found that approximately 1.4 per cent of the progeny of one 
trisome were trisomic from the cross 2n I 2n + 1. Rhoades ( 26 ) found no 
trisomics in a population of 1845 plants of a similar cross involving a 
different trisome of corn. 

In common barley Smith (28) found trisomics in a diploid stock, 
the origin of which he attributed to a 6:8 chromosome segregation at 
meiosis. Later, Ramage (25) noted that an interchange was carried by the 
same stock and concluded that Smith’s trisomics likely were the result 
of a 3:1 separation from a ring of four chromosomes. Although the 
trisomics from this material were shorter than normal, they were 
vigorous and had no distinguishing characteristics. In 1952 Tsuchiya (31) 
recovered six trisomic plants among the progeny of a hypotriploid plant. 

They differed from each other and from diploids in several characteristics, 
including plant height; stem thickness; number of tillers; length, width 
and color of leaves; shape of heads; habit of growth; time of maturity; 
fertility; and cytological behavior. The most striking characteristic 
among the trisomics was their fertility, which varied from zero to 92 
per cent under self-fertilization. 

In 1955 Ramage (25) was the first to report on the morphological 
and cytogenetical identification of barley trisomics. He isolated primary 
and secondary trisomics from interchanges involving each of the seven 







i t • a! • 

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67 


chromosomes of the variety Mars. The morphological descriptions of 

the trisomic types found to be genetically associated with specific 

chromosomes were given as follows: 

■Trisome of Chromosome a 1 .- This type was 
weak, dwarf and highly sterile. 

Trisome of Chromosome b .- This type had 
narrow, dark-green leaves. 

Trisomes from Interchange c - d .- One type was 
dwarf with slender stems and short, narrow leaves; 
it was completely self-sterile; most spikes did 
not reach the heading stage. The second type from 
this interchange was later in maturity than normal 
but otherwise was indistinguishable from diploid sibs. 

Trisomes from Interchange e - f .- One type 
was dwarf with short, wide leaves, particularly the 
flag leaves. The other type was readily distinguished 
by the long, narrow, light-green, drooping leaves. 

Trisome of Chromosome g .- This type was 
not readily distinguished from diploid 
sibs, although it produced fewer tillers. 


Burnham and Hagberg (10) have summarized the results obtained 
by Eamage and by several other workers ?dio have utilized trisomics and 
translocation stocks to determine the association of barley linkage 
groups with their respective chromosomes. The evidence establishes the 
independence of all linkage groups except III, VII, and V, on the one 
hand, and II and V on the other. No genes have been located on 
chromosome jg; Burnham and Hagberg suggested the possibility that a and d 
also have no known genetic markers. According to their summerization, the 

following associations appear probable at the present time: 

Chromosome f b c e a g d 

Linkage Group I III VI IV II? - V? 

VII 


The seven barley chromosomes have been designated 
temporarily by the small letters a to £ by Burnham et al. (ll). 











«f 














• ' 

01 ? 











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68 


MATERIALS AND METHODS 

Primary trisomics described in this part of the study were 
obtained from the progenies of the hybrid and Gateway triploids discussed 
in the first part. Each original trisomic plant was cytologically 
identified as such and affixed with a 1 T* number. All trisomic 
descendents of each original trisomic plant retained this number. The 
morphological descriptions are based on data and notes taken on the 
original trisomics and their trisomic progenies grown in the field in 
two different years. Measurements on maximum leaf width and length 
were taken on the three uppermost leaves of the original trisomic plants 
and diploid sibs. Data on spike density were taken on a minimum of 
19 spikes collected from six or more plants of each trisomic type and 
from the diploid. Data on the number of days required to head are based 
on a minimum of six plants, while the average values for plant height were 
determined from not less than five plants. All measurements were made on 
plants grown in the field in 1955 > except of leaf width and length, 
which were obtained from plants grovjn in the greenhouse. 

The varieties Nigrinudum I and Golsess V were used as tester 
stocks to determine the association of Gateway trisomic type T39 with 
its corresponding linkage group. These two tester stocks together possess 
at least one contrasting marker gene for the corresponding locus in 
Gateway for each of the linkage groups. The characters used, their 
symbols, the linkage group to which each has been assigned (29) and the 
genotype of Gateway are summarized in Table I. The two genetic stocks 
were used as pollen parents in crosses with trisomic plants. Seeds from 






69 


trisomic plants were space-planted to facilitate classification 
for seedling characters. Individual F^ plants were classified for 
each segregating character. Tests for association were made by 
analysis of populations for disomic and trisomic ratios. 

TABLE I 


Linkage groups and marker genes involved in 
tests for association with Gateway trisomic T39 


Linkage group 

Character 

Gene 

symbol 

Genotype 
of Gateway 

I 

Two-row vs. six-row spike 

V, v 

w 

II 

Black vs. white pericarp 
and lemma 

B, b 

bb 

III 

Covered vs. naked caryopsis 

N, n 

NN 

IV 

Hooded vs. awned spike 

K, k 

kk 

IV 

Blue vs. white aleurone 

Bl, bl 

blbl 

V 

Rough vs. smooth awns 

R, r 

rr 

VI 

Normal vs. albino seedlings 

A n> a n 

Vn 

VII 

Normal vs. chlorina seedlings 

F , f 
c ; c 

o 

o 


OBSERVATIONS AND RESULTS 

Morphological Characteristics of Primary Trisomics 

Primary trisomic plants obtained from the progeny of the 
triploids differed from one another and from diploid sibs in characteristics 
such as rate of growth; relative vigor; height; length, width and 







' 








. 


u 






■ 

. . 










.) -J 












70 


color of leaves; degree of tillering; and length and density of the spike. 

Although a few of the trisomic types derived from the hybrid triploids 

appeared to have certain distinct characteristics, it was difficult or 

impossible to distinguish these trisomics morphologically from one another 

and in some instances from the diploids because of the high degree of 

heterozygosity present in the original stocks. One type, however, differed 

conspicuously from all others and from the diploids by having extremely 

long, narrow, drooping leaves with enlarged auricles and ligules. This 

also was the only type that could be distinguished in the seedling stage. 

A similar type occurred among the trisomic progeny of the Gateway triploids* 

Since the Gateway trisomics were derived from a pure line stock, 

morphological differences among them could be attributed to the effects of 

specific chromosomes when present in triplicate. 

On the basis of the data on some measurable characteristics 

given in Table II and on additional visual differentiating characteristics, 

four Gateway trisomic types could be readily distinguished from one 

another and from diploids. Compared with diploids, all trisomic types 

were shorter, later in heading, had fewer tillers and were considerably 

lower in fertility. Specific differences between the four types and 

between these and the diploids were as follows 2 

Type T31(Fig, l) .- Leaves darker green, 

broader and more erect than diploid; neck distinctly 

coiled (Fig. 2); head relatively short and dense 

when compared with diploid and other trisomics; 

awns appressed rather than spreading; 

tallest of the four trisomics. 

Type T39(Fig. 3 ) .-Spike shorter but more lax 
than diploid and tended to be tapered from base 
toward apex, rather than oblong in shape; leaves 
shorter and narrower than normal and rolled under 
at the margins, particularly toward the apex; 
compared with other trisomics, this type had the 





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of Gateway trisomic types 


71 











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72 


longest spike, was most prolific in stooling and had 
the greatest fertility. 

Type T46 .- Leaves extremely long, narrow and 
drooping with relatively large auricles and 
ligules; head emerged from the side of flag leaf. 

Type T51 (Fi g- /|)-~ Leaves very broad relative to 
length, particularly the flag leaf, dark blue-green 
in color, erect, and base tended to clasp the thick 
stem; florets were small and flaccid at the heading 
stage with supernumery organs on the upper ones; at 
emergence from sheath the awns projected in all 
directions giving spike a ragged appearance. 

The original trisomic type T46 from the Gateway stock was lost because 

of high sterility. However, a very similar type (previously referred to), 

probably trisomic for the same chromosome, was recovered from the 

hybrid material; it reproduced readily under open-pollination. 

When all of the adult characteristics of each Gateway trisomic 

type were taken into consideration, it was relatively easy to distinguish 

them from each other and from the diploid under field conditions. In the 

greenhouse certain of the differentiating features tended to be modified 

or absent. For example, T51 did not show the extremely broad, dark-green 

leaves and thick stems in the greenhouse, and the development of the 

head and florets was more normal, facilitating emasculation and hand- 

pollination. 


Fertility of Trisomics 

The fertility among 14 original trisomic plants obtained from 
the progeny of the hybrid triploids ranged from about 20 to 67 per cent 
and averaged 46 per cent under open-pollination in the greenhouse. The 
average fertility of nine diploid sibs was about 92 per cent. Twelve 
additional trisomics obtained from the same source but grown in the field 
had a fertility from zero to approximately 92 per cent, with an average of 
about 52 when open-pollinated. Two of the 26 trisomic plants were 















r 











■ 


\ DO' 
















'i .. ... 3 









73 



ig.l. Trisomic type T31 and diploid Gateway. 
ig.2. Trisomic type T31 (left)showing coiled neck and 
diploid Gateway (right). 

Fig. 3 . Trisomic type T39 and diploid Gateway. 

Fig. 4 . Trisomic type T51 diploid Gateway. 






















74 


completely self-sterile. The self-fertility of three morphologically 
distinct Gateway trisomic types and the diploid when grown in the 
field is given in Table III. Type T31 had the lowest fertility with 
a seed set of about 17 per cent, while 'Type T39 was highest with about 
50 per cent. 


TABLE III 

Fertility of open-pollinated Gateway trisomics 
and the diploid 


Trisomic 

type 

No. of 
plants 

No. of 
florets 

No. of 
seeds 

% 

fertility 

T31 

6 

1014 

170 

16.8 

T39 

9 

1575 

789 

30.1 

T51 

4 

246 

_ 2 i 

37.0 



2835 

1050 

Av. 37.0 

Diploid 

6 

663 

637 

96.1 


Transmission of Trisomics 

Data on the frequency of trisomic plants among progenies of 
open-pollinated trisomics are shown in Table IV. Trisomic plants were 
distinguished from diploids in the hybrid progenies by lack of vigor, 
short growth, lateness, sterility and certain morphological characteristics 
that were known from previous experience to differentiate them. In a few 
instances trisomic plants were cytologically verified. The Gateway 
trisomics were readily identified from diploid sibs by the morphological 
characteristics already described. The frequency of trisomic plants 










; '■ .LX ;.'j J' foulS xh 

- 

. . ■ ■ ■ . 






















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75 


TABLE IV 

Frequencies of transmission of 
trisomic plants in progenies of open-pollinated trisomics 


Trisomic 
. type 

Total no. of 

2 n *• 1 and 2 n 

No. of 

2 n + 1 

Per cent 
2 n -f 1 

Hybrids 

T4-2 

35 

8 

22.9 

T5-1 

56 

10 

17.9 

T6-2 

51 

9 

17.6 

T10-2 

19 

4 

21.1 

112-1 

98 

25 

25.5 

215-1 

56 

14 

25.0 

T16-1 

18 

4 

22.2 

T 21 

45 

14 

31.1 

T22 

24 

6 

25.0 

T23 

12 

4 

33.3 

T26 

49 

18 

36.7 

127 

20 

4 

20.0 

T28 

17 

4 

23.5 

T29 

36 

6 

16.7 

130 

26 

_Z 

26.9 


562 

137 

Av. 24*4 

Gateway 

131 

61 

15 

24.6 

139 

72 

19 

26.4 

T51 

J& 


21.4 


175 

43 

Av. 24-6 










































. 


* 





. 









: 
















76 


among the progenies of open-pollinated hybrid types ranged from 16.7 
to 36.7 per cent, averaging 24.4. The frequencies of transmission among 
the progenies of the three morphologically identified Gate-way types 
T31, T39 and T51 were 24.6, 26.4 and 21.4 per cent, respectively. 

Limited data were obtained on the frequency of transmission 
of the extra chromosome through the pollen. Of 237 plants from the cross 
2n X 2n +• 1, involving five hybrid trisomic types and four diploid 
varieties, only one trisomic plant was cytologically identified (fable V) 


TABLE V 

Frequencies of transmission of 
trisornics in progenies of 2n X 2n + 1 


Trisomic 

type 

Total no. of 

2n + 1 and 2n 

No. of 

2n + l 

% of 
2n + 1 

T12-1 

51 

0 

0.0 

T15-1 

67 

1 

1.5 

T21 

68 

0 

0.0 

T22 

32 

0 

0.0 

T27 

-12 

0 

0.0 


237 

1 

Av. 0.4 


Cytogenetic Identification of Gateway 
Trisomic T39 

Tests were completed for the cytogenetic identification of 
Gateway trisomic type T39. The observed F 2 segregations for each of 
the marker genes were tested for deviations from a 3 si ratio. The T 
analysis of the data in Table VI indicates disomic inheritance for 





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77 


TABLE VI 


X 2 


analysis of 


F 2 populations of crosses between trisomic 
T39 and tester stocks for 3*1 disomic segregations 


Linkage 

group 

I 


II 


III 


IV 


IV 


V 


VI 


Marker _ Frequency 


gene 

Observed 

Calculated 

IT 

P 

V 

V 

281.00 

89.00 

277.50 

-22.-5Q 

0.04 

0.13 



370.00 

370.00 

0.17 

0.95-0.50 

B 

b 

226.00 

no-op 

274.50 

-SLL-5Q 

8.57 

25LZ1 



366.00 

366.00 

34.28 

< 0.001 

N 

n 

272.00 

95.00 

275.25 

-21*25 

0.04 

0.12 



367.00 

367.00 

0.16 

0 . 95 - 0.50 

K 

k 

233.00 

84.00 

237.75 

79.25 

0.09 

0.29 



317.00 

317.00 

0.38 

0 . 95 - 0.50 

B1 

bl 

98.00 

40.00 

O O 

ITN U-\ 

. * 

<r\ -4 1 

O 

1—1 

0.29 

0.88 



138.00 

138.00 

1.17 

0 . 30 - 0.20 

R 

r 

351.00 

103.00 

340.50 

m-ip. 

0.32 

0.97 



454.00 

454.00 

1.29 

0 . 30 - 0.20 

a n 

297.00 

90.00 

290.25 

96-7,5 

1.18 

0.54 



387.00 

387.00 

0.72 

0 . 50 - 0.30 


267.00 

82.00 

261.75 

87.25 

0.11 

0^22 



349.00 

349.00 

0.43 

0 . 95 - 0.50 


VII 



































* 

. 





. 







78 


all markers except B, b, located in Linkage Group II. The observed 

segregation for this factor was then tested for goodness of fit to a 

trisomic ratio based on the assumption of nontransmission of n + 1 

pollen, 25 per cent transmission of n + 1 female gametes, and 

chromosome segregation. On this basis 7/18 of the F 2 are expected 

2 

to be homozygous recessive. The X analysis in Table VII shows 
a good fit of observed to calculated values, indicating trisomic 
inheritance for B, b. 'The analj^sis of the data in Tables VI and VII, 
therefore, establishes the association of trisomic type T39 with 
Linkage Group II and its independence of the other known groups. 

TABLE VII 


X analysis of Fp population for 11:7 
trisomic segregation of B, b in Linkage 
Group II 


Marker gene 

Frequency 

xL 

Observed 

Calculated 

B 

226.00 

223.70 

0.02 

b 

140.00 

142.30 

0.0 u 


366.00 

366.30 

0.06 


P = 0.95 - 

0.50 



IIoGUSSIGN 

Gn the basis of the descriptions of the trisomics of the 
variety Mars and their associations with certain chromosomes, as given 
by Ramage (25), it is possible to indicate which of the four Gateway 
trisomic types likely correspond with specific chromosomes. Trisomic 
type T39 of the variety Gateway was genetically identified with Linkage 












79 


Group II and shown to be independent of the remaining known groups. 
Therefore, according to the probable associations between the chromosomes 
and linkage groups indicated by Burnham and Hagberg (10), type T39 
should be trisomic for chromosome a* However, the morphological 
description given by Ramage for this trisomic does not agree with that 
for T39. Fossibly the morphological characteristics expressed by a 
certain chromosome when in triplicate vary from variety to variety. For 
example, Ramage observed no trisomic type in Mars with a coiled neck 
(personal communication), a characteristic that was very distinct and 
invariable f° r type T31 of Gateway. Otherwise, the latter type appears 
to correspond to Ramage 1 s trisome of either chromosome c or d, on the one 
hand, or g on the other; more likely it is the trisome of g, since this 
type produced fewer tillers, which was also a characteristic of 131 • 

Ramage*s two trisomic types involving chromosomes e and f (the two types 
were not specifically identified as to which of these two chromosomes 
was associated with each) probably correspond to Gateway trisomic types 
T 46 , which had long, drooping leaves, and to T51, which approached 
dwarfness under field conditions and had short, broad leaves, particularly 
the flag leaves. 

In accordance with the findings on trisomics of other species 
(3, 15, 16, 27), the frequency of trisomic plants among the progenies of 
open-pollinated barley trisomic types was considerably less than the 
theoretical 50 per cent, approaching an average of 25 per cent in the present 
study. Limited results also indicated that the extra chromosome was 
transmitted through the pollen with a frequency of less than one per cent; 
therefore, it is probable that transmission of trisomics in barley is 





ifl ‘..J la 






■j 










. 


4 ; 










so 


largely, if not entirely, through female gametes, at least for 
certain chromosomes. This is also in agreement with the results 
reported in Datura (9), Nicotiana (16), and corn (22, 26). 

Both Tsuchiya (31) and Ramage (25) found that certain simple 
trisomic types obtained from pure varieties of barley were completely 
self-sterile. In the present study two of 26 original hybrid and two 
of 12 Gateway primary trisomic plants were completely sell-sterile. 

Two additional trisomics of Gateway were lost because of almost complete 
self-sterility. This evidence indicates that certain of the primary 
trisomes of common barley, particularly if established in a pure variety, 
are completely self-sterile, or nearly so. They would have to be maintained 
by hand-pollination with pollen from diploids of the same variety or, as 
suggested by Ramage (25)* maintained as heterozygous stocks, since 
trisomics from intervarietal crosses are more highly fertile. 

SUMMARY 

1. Four morphologically distinct primary trisomic types 
of the variety Gateway were identified. 

2. The fertility of each of three Gateway trisomic types 
under open-pollination was approximately 17* 37 and 50 per cent, 
respectively, averaging approximately 37 per cent. 

3. The frequency of trisomic plants among progenies of 15 
unidentified open-pollinated hybrid trisomic types varied from about 
17 to 37 per cent and averaged 2U per cent. In progenies of three 
open-pollinated, morphologically distinct Gateway trisomic types approx¬ 
imately 21, 25 and 26 per cent of the plants were trisomic, respectively. 









T2 












■ i 


, 









81 


4* Transmission of the extra chromosome through the pollen 
of five unidentified hybrid trisomics averaged 0.4 per cent in a total 
population of 237 plants. 

5. One Gateway trisomic type was found to be associated 
with Linkage Group II and independent of the other known groups. 






82 


REFERENCES 


PART Is TRIPLOIDS 


1* AASE, HANNAH C. Cytology of 'friticum , Secale , and Aegilops hybrids 
with reference to phylogeny. Research Studies State Coll. 

Wash. 2:5-60. 1930. 

2. _. Cytology of cereals. II. Botan. Rev. 12:255-334. 1946. 

3. ASHMAN, R.B. and BOYLE, W.S. A cytological study of the induced 

octoploid of an Agropyron-Hordeum hybrid. J. Heredity, 

46:297-301. 1955. 

4. AVERS, CHARLOTTE J. Chromosome behavior in fertile triploid Aster 

hybrids. Genetics, 39:117-126. 1954- 

5. BELLING, JOHN. The behavior of homologous chromosomes in a triploid 

Ganna . Proc. Natl. Acad. Sci. 7:197-201. 1921. 

6. _. Homologous and similar chromosomes in diploid and 

triploid hyacinths. Genetics, 10:59-71. 1925. 

7* _______ . 'The attachments of chromosomes at the reduction 

division in flowering plants. J. Genetics, 18:177-205. 1927. 

8. _______ and BLAKESLEE, A. F. The assortment of chromosomes 

in triploid Daturas . Am. Nat. 56:339-346. 1922. 

9. _______ . The reduction division in haploid, 

diploid, triploid and tetraploid Daturas . Proc. Natl. Acad. 

Sci. 9:106-111. 1923. 

10. __j and FARNHAM, M. E. Inheritance 

in tetraploid Daturas . Botan. Gaz. 76:329-373. 1923. 

11. BOYLE, W.S. and HOLMGREN, A.H. A cytogenetic study of natural and 

controlled hybrids between Agropyron trachycaulum and 
Horde urn .jubatum . Genetics, 40:539-545- 1955. 

12. BUCHH0LZ, J.T. and BLAKESLEE, A.F. Pollen-tube growth in crosses 

between balanced chromosomal types of Datura stramonium . 

Genetics, 14:536-568. 1929. 

13. CHANDLER, C., PORTERFIELD, W.M., and STOUT, A.B. Microsporogenesis 

in diploid and triploid types of Lilium tigrinum with special 
references to abortions. Cytologia, Fujii Jubilee, 2:756-764. 

1937. 

14. CHIN, T.C. Cytology of autotetraploid rye. Botan. Gaz. 104:627-632. 

1943. 































83 


15* COOPER, D.C. Caryopsis development following matings between 

diploid and tetraploid strains of Zea mays. Am. J. Botany, 
38:702-708. 1951. 

16* ___ and BRINK, R.A. Seed collapse following matings 

between diploid and tetraploid races of Lycopersicon 
pimpinellifolium . Genetics, 30:376-401. 1945. 

17. DARK, S.O.S. Chromosome associations in triploid Primula sinensis. 

J. Genetics, 25:91-95. 1932. 

18. DARLINGTON, C.D. Meiosis in polyploids. II. Aneuploid hyacinths. 

J. Genetics, 21:17-56. 1929. 

19. _. Meiosis in diploid and tetraploid Primula sinensis. 

J. Genetics, 24:65-96. 1931. 

20. _. Recent advances in cytology. P. Blakiston’s 

Son and Company, Inc., Philadelphia. 1937. 

21. DERMEN, HAIG. Polyploidy in Petunia . Am. J. Botany, 18:250-261. 

1931. 

22. EAST, E.M. The behavior of a triploid in Nicotiana tabacum L. 

Am. J. Botany, 20:269-289. 1933. 

23. FRANKEL, O.H. A self-propagating structural change in frit i cum . 

Heredity, 3:163-194. 1949. 

24. GAJZKSKI, W. On the behavior of univalents of meiosis in some 

interspecific Geum hybrids. Hereditas, 35:221-241. 1949. 

25. HAKANSS0N, A. and SLLERSTROM, 3. Seed development after reciprocal 

crosses between diploid and tetraploid rye. Hereditas, 
36:256-296. 1950. 

26. JONES, R.E. and BAMF0RD, R. Chromosome number in the progeny of 

triploid Gladiolus with special reference to the contribution 
of the triploid. Am. J. Botany, 29:807-813. 1942. 

27* KIHARA, H. Conjugation of homologous chromosomes in the genus 

hybrids Triticum x Aegilops and species hybrids of Aegilops . 
Cytologia, 1:1-15. 1929. 

28. K0ST0FF, D0NTCH0. The problem of haploidy (Cytogenetic studies on 

Nicotiana haploids and their bearings to some other cytogenetic 
problems). Bibliographica Genetica, 13:1-148. 1941. 

29. LAMM, ROBERT. Chromosome behavior in a triploid rye plant. 

Hereditas, 30:137-144. 1944* 

30. LESLEY, J.W. A cytological and genetic study of progenies of triploid 

tomatoes. Genetics, 13:1-43* 1928. 



























84 


31 . LESLEY^ MARGARET MANN. Maturation in diploid and triploid tomatoes. 

Genetics, 11:267-279. 1926. 

32. LOVE, R.M. Chromosome behavior in F-, -wheat hybrids. I. Pentaploids. 

Gan. J. Research, C, 19:351-3697 1941. 

33* McCLINTCCK, BARBARA. A cytological and genetical study of triploid 
maize. Genetics, 14:180-222. 1929. 

34* MELBURNj MYRTLE C. and THOMPSON, W.P. The cytology of a tetraploid 
wheat hybrid ( Triticum spelta x T. monococcum). Am. J. Botany, 

14:327-333. 1927. 

35- MJNTZING, A. Studies on meiosis in diploid and triploid Solanum 
tuberosum L. Hereditas, 17:223-245* 1933. 

36. _. Polyploidy from twin seedlings. Cytologia, Fujii 

Jubilee, 1:211-227. 1937. 

37. _ . Note on heteroploid twin plants from eleven genera. 

Hereditas, 24:487-491. 1938. 

38 . MYERS, W.M. Cytological studies of a triploid perennial ryegrass 

and its progeny. J. Heredity, 35:17-23. 1944. 

39. _. The randomness of chromosome distribution at anaphase I 

in autotriploid Lolium perenne L. Bull. Torrey Botan. Club, 
71:144-151. 1944. 

40. __. Meiosis in autotetraploid Lolium perenne in relation to 

chromosomal behavior in autopolyploids. Botan. Gaz. 106:304-316. 
1945* 

41. __. Cytology and genetics of forage grasses. Botan. Rev. 

13:319-421. 1947. 

42. NEKTON, W.C.F. and DARLINGTON, C.D. Meiosis in polyploids. I. 

Triploid and pentaploid tulips. J. Genetics, 21:1-16. 1929. 

43. NI3HIYAMA, I. The genetics and cytology of certain cereals. VI. 

Chromosome behavior and its bearing on inheritance in triploid 
Avena hybrids. Mem. Coll. Agr. Kyoto Imp. Univ. No. 32. 1934. 

44. N0RDEN3KT0LD, HEDDA. Cytological studies in triploid Phleum . 

Botan. Notiser, 1941: 12-32. 1941. 

45. O'MARA, J.G. Meiosis in autotetraploid Secale cereale . Botan. Gaz. 

104:563-575. 1943. 

46 . PERSON, CLAYTON. An analytical study of chromosome behavior in a 

wheat haploid. Can. J. Botany, 33 : ll-30. 1955* 

47. FUNJASINGH, KRUI. Chromosome numbers in crosses of diploid, triploid 

and tetraploid maize. Genetics, 32:541-554. 1947. 


































48. 


85 


RANDOLPH, L.F. Cytogenetics of tetraploid maize. J. Agr. Research, 
50:591-605. 1935. 

49* RHOADES, M.M. and McCUNTOCK, BARBARA. The cytogenetics of maize. 

Botan. Rev. 1:292-325. 1935. 

50. RICK, CHARLES M. A survey of cytogenetic causes of unfruitfulness 

in the tomato. Genetics, 30:347-362. 1945. 

51. SATINA, SOPHIA and BLAKESLKB, A.F. Chromosome behavior in triploids 

of Datura stramonium . I. The male gametophyte. Am. J. Botany, 
24:518-527. 1937. 

52. _. Chromosome behavior in triploid 

Datura. II. The female gametophyte. Am. J. Botany, 24:621-627. 
1937. 

53. SAX, KARL. Sterility in -wheat hybrids. II. Chromosome behavior 

in partially sterile hybrids. Genetics, 7:513-552'. 1922. 

54. _ and SAX, HALLY J. Chromosome behavior in a genus cross. 

Genetics, 9:454-464. 1924. 

55* SEARS, E.R. Misdivision of univalents in common wheat. Gliromosoma, 
4:535-550. 1952. 

56. SMITH, LUTHER. Cytology and genetics of barley. Botan. Rev. 

17:1-355. 1951. 

57. SMITH, S.G., HUSKIES, C.L., and SANDER, G.F. Mutations in polyploid 

cereals. II. The cytogenetics of speltoid wheats. Can. J. 
Research, C, 27**348-393. 1949. 

58. SWANSON, CARL P. Cytology and cytogenetics. Prentice-Hall, Inc., 

Englewood Cliffs, N.J. 1957* 

59. THOMPSON, W.P. Chromosome behavior in triploid wheat hybrids. 

J. Genetics, 17:43-48. 1926. 

60. _ . The cytology of species hybrids in wheat. Sci. Agr. 

8 : 56 - 62 . 1927. 

61. _ t . Cytology and genetics of crosses between fourteen- 

and seven-chromosome species of wheat. Genetics, 16:309-324* 

1931. 

62. T0MET0RP, G. Cytological studies on haploid Ilordeum distichum . 

Hereditas, 25:241-254. 1939. 

63 . TSUCHIYA, TAKUH. Cytogenetics of a hypotriploid barley and its progeny. 

Mem. Beppu Womens Univ. 2:19-42. 1952. 

64 . _. Cytogenetic studies of a triploid hybrid plant 

in barley. Rept. Kihara Inst. Biol. Research, No. 5:78-93* 

1952. 




































86 


65 • CPCOii^ MARGARET. The cytology of triploid and tetraploid 
Lycopersicum esculentum . J. Genetics, 31:1-19. 1935. 

66. WATKINS, A.E. Hybrid sterility and incompatibility. J. Genetics, 
25:125-162. 1932. 


PART II: TRISOMICS 


1. BLAKESLEE, A.F. New Jimson weeds from old chromosomes. J. Heredity, 
25:80-108. 1934. 

2* _ and AVERY, B.T., JR. Mutations in the Jimson weed. 

J. Heredity, 10:111-120. 1919. 

3* __ and AVERY, A.G. Fifteen-year breeding records of 

2n + 1 types in Datura stramonium . Co-operation in Research. 
Carnegie Inst. Wash. Publ. 501:315-351. 1938. 

4* _ and FARNHAM, M.E. Trisomic inheritance in the Poinsettia 

mutant of Datura . Am. Nat. 57:481-495* 1923. 

5* __, BELLING, JOHN., and FARNHAM, M.E. Chromosomal 

duplication and Mendelian phenomena in Datura mutants. Science, 
52:388-390. 1920. 

6. BELLING, JOHN., and BLAKESLEE, A.F. The assortment of chromosomes 

in triploid Daturas. Am. Nat. 56:339-346. 1922. 

7. ____. The reduction division in haploid 

diploid, triploid and tetraploid Daturas. Proc. Natl. Acad. 

Sci. 9:106-111. 1923. 

8. BUCHHOLZ, J.T. and BLAKESLEE, A.F. Pollen-tube growth in crosses 

between balanced chromosomal types of Datura stramonium . 

Genetics, 14:538-568. 1929. 

9. __ . Pollen-tube growth in primary 

and secondary 2n + 1 Daturas . Am. J. Botany, 19:604-646. 1932. 

10. BURNHAM, C.R. and HAGB2RG, A. Cytogenetic notes on chromosomal 

interchanges in barley. Hereditas, 42:467-482. 1956. 

11. ___, .VHITE, F.H., and LIVERS, R. Chromosomal interchanges 

in barley. Cytologia, 19:191-202. 1954. 

12. CLAUSEN, R.E. and G00DSPEED, T.H. Inheritance in NIcotiana tabacum . 

IV. The trisomic character "Enlarged.” Genetics, 9:181-197. 

1924. 


13 


BERMEN, HAIG. Polyploidy in Petunia . Am. J. Botany, 18:250-261. 1931< 

























14 


87 


. EAST, E.M. The behavior of a triploid in Nicotiana tabacum L. 

Am. J. Botany, 20:269-289. 1933. 

15* EINSET, J. Chromosome length in relation to transmission frequency 
of maize trisomes. Genetics, 28:349-364. 1943* 

16. GOODSPEED, T.H. and AVERY, P. Trisomic and other types in Nicotiana 

sylvestris . J. Genetics, 38:381-458. 1939. 

17. LESLEY, J.W. The genetics of Lycopersicum esculentum . Mill. I. The 

trisomic inheritance of "Dwarf." Genetics, 11:352-354* 1926. 

18. _. A cytological and genetic study of progenies of triploid 

tomatoes. Genetics, 13:1-43. 1928. 

19. _Trisomic types of the tomato and their relation to 

the genes. Genetics, 17:545-559. 1932. 

20. __. Crossing-over in tomatoes trisomic for the ’A' or first 

chromosome. Genetics, 22:297-306. 1937* 

21. McCLINTOCK, BARBARA. A cytological and genetical study of triploid 

maize. Genetics, 14:180-222. 1929. 

22. _____ and HILL, HENRY E. The cytological identification 

of the chromosome associated with the R-G linkage group in 
Zea mays . Genetics, 16:175-190. 1931. 

23. MYERS, W.M. Cytological studies of a triploid perennial ryegrass 

and its progeny. J. Heredity, 35:17-23* 1944. 

. 24. RJNJASINGH, KRUI. Chromosome numbers in crosses of diploid, triploid 
and tetraploid maize. Genetics, 32:541-554* 1947. 

25. RAMAGE, R.T. The trisomics of barley. Ph.D. Thesis, University of 

Minnes ot a. 1955* 

26. RHOADES, M.M. A secondary trisome in maize. Proc. Natl. Acad. Sci. 

19 :1031-1038. 1933. 

27. RICK, CHARLES M. and BARTON, DONALD W. Cytological and genetical 

identification of the primary trisomics of the tomato. 

Genetics, 39:640-666. 1953* 

28. SMITH, LUTHER. An inversion, a reciprocal translocation, trisomics 

and tetraploids in barley. J. Agr. Research, 63:741-750. 1941. 

29. . Cytology and genetics of barley. Botan. Rev. 

17:1-355. 1951. 

30. TAGAKI, F. Karyogenetical studies on rye. I. A trisomic plant. 

Cytologia, 6:496-501. 1935* 

31. TSUCHIYA, TAKUMI. Cytogenetics of a hypotriploid barley and its 

progeny. Mem. Beppu Aomen’s Univ. 2:19—42. 1952*